Math & Science Cheat Sheet: Basic Math, Pre-Algebra, Sequences, Geometry, Summaries of Mathematics

Download Math & Science Cheat Sheet: Basic Math, Pre-Algebra, Sequences, Geometry and more Summaries Mathematics in PDF only on Docsity! This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 1 MATH CHEAT SHEET Basic Math and Pre-Algebra Cheat Sheet Groups of Numbers • Natural or counting numbers: 1, 2, 3, 4, … • Whole numbers: 0, 1, 2, 3, … • Integers: …-3, -2, -1, 0, 1, 2, 3, • Rational numbers: Integers and fractions. • Irrational numbers: Cannot be written as fractions: √3 or π. • Prime numbers: Divisible only by 1 and itself: 2, 3, 5, 7, 11, 13, … (0 and 1 are not prime or composite.) • Composite numbers: Divisible by more than just 1: 4, 6, 8, 9, 10, 12, … Properties of Addition and Multiplication • Closure: All answers fall into original set. • Commutative: Order does not make any difference: a + b = b + a, ab = ba. • Associative: Grouping does not make any difference: (a + b) + c = a + (b + c), (ab)c = a(bc). • Identity: 0 for addition, 1 for multiplication. • Inverse: Negative for addition, reciprocal for multiplication. Order of Operations 1. Work within parentheses ( ), brackets [ ], and braces { } from innermost and work outward. 2. Simplify exponents and roots working from left to right. 3. Do multiplication and division, whichever comes first left to right. 4. Do addition and subtraction, whichever comes first left to right. Rounding Off 1. Underline the place value to which you're rounding off. 2. Look to the immediate right (one place) of your underlined place value. 3. Identify the number (the one to the right). If it is 5 or higher, round your underlined place value up 1 and change all the other numbers to its right to zeros. If less than 5, leave your underlined place value as it is and change all the other numbers to the right to zeros. Decimals • To add or subtract decimals, simply line up the decimal points and then add or subtract as usual. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 2 • To multiply decimals, just multiply as usual and then count the total number of digits above the line that are to the right of all decimal points. Place the decimal point in your answer so that there are the same number of digits to the right of the decimal point as there are above the line. • To divide decimals, if the number you're dividing by has a decimal, move the decimal to the right as many places as possible and then move it under the division sign just as many places (add zeros if necessary). Move the decimal up to your answer. Fractions To add or subtract fractions, you must have a common denominator. • If two fractions have a common denominator (these are called like fractions), you simply add or subtract the numerator and keep the same denominator. (For example, 1/5 + 2/5 = 3/5.) • If two fractions do not have a common denominator (unlike fractions), find a lowest common denominator (LCD), change each of the fractions to equivalent fractions with the new denominator, and then add or subtract the numerators and keep the same denominator. (For example, 1/2 + 1/3 = 3/6 + 2/6 = 5/6) • When subtracting mixed numbers, you may have to "borrow" from the whole number. When you borrow 1 from the whole number, the 1 must be changed to a fraction. • To multiply fractions, simply multiply the numerators and then multiply the denominators. (For example, 2/3 × 1/5 = 2/15.) Reduce to lowest terms if necessary. • To divide fractions, invert the second fraction and then multiply. (For example, 1/5 ÷ 1/4 = 1/5 × 4/1 = 4/5.) A additive inverse: The opposite (negative) of a number. Any number plus its additive inverse equals 0. associative property: Grouping of elements makes no difference in the outcome. This is only true for multiplication and addition. B braces: Grouping symbols used after the use of brackets; signs { } used to represent a set. brackets: Grouping symbols [ ], used after the use of parentheses. C canceling: In multiplication of fractions, dividing the same number into both a numerator and a denominator. circumference: The distance around a circle; equals 2 × π × the radius or π × the diameter (C = 2πr or πd). closure property: When all answers fall into the original set. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 5 multiples: Numbers found by multiplying a number by 2, by 3, by 4, and so on. multiplicative inverse: The reciprocal of a number. Any number multiplied by its multiplicative inverse equals 1. N natural number: A counting number; 1, 2, 3, 4, and so on. negative number: A number less than 0. number series: A sequence of numbers with some pattern. One number follows another in some defined manner. numerator: The top symbol or number of a fraction. O odd number: An integer not divisible by 2. operation: Multiplication, addition, subtraction, or division. order of operations: The priority given to an operation relative to other operations. For example, multiplication is performed before addition. P parentheses: Grouping symbols ( ). percent or percentage: A common fraction with 100 as its denominator. For example, 37% is 37/100. permutations: The total number of dependent choices. place value: The value given a digit by the position of a digit in the number. positive number: A number greater than zero. power: A product of equal factors. 4 × 4 × 4 = 43, reads "four to the third power" or "the third power of four." Power and exponent are some× used interchangeably. prime number: A number that can be divided by only itself and one. probability: The numerical measure of the chance of an outcome or event occurring. product: The result of multiplication. proper fraction: A fraction in which the numerator is less than the denominator; for example, 2/3. proportion: Written as two equal ratios. For example, 5 is to 4 as 10 is to 8, or 5/4 = 10/8. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 6 Q quotient: The result of division. R range: The difference between the largest and the smallest number in a set of numbers. ratio: A comparison between two numbers or symbols; may be written x:y, x/y, or x is to y. rational number: An integer or fraction such as 7/8 or 9/4 or 5/1. Any number that can be written as a fraction x/y with x a natural number and y an integer. real number: Any rational or irrational number. reciprocal: The multiplicative inverse of a number. For example, 2/3 is the reciprocal of 3/2. reducing: Changing a fraction into its lowest terms. For example, 2/4 is reduced to 1/2. rounding off: Changing a number to the nearest place value as specified; a method of approximating. S scientific notation: A number between 1 and 10 and multiplied by a power of 10, used for writing very large or very small numbers; for example, 2.5 × 104. square: The result when a number is multiplied by itself. square root: A number that when multiplied by itself gives you the original number; its symbol is √. For example, 5 is the square root of 25; √25 = 5. sum: The result of addition. T tenth: The first decimal place to the right of the decimal point. For example, .7 is seven- tenths. W weighted mean: The mean of a set of numbers that have been weighted (multiplied by their relative importance or × of occurrence). whole number: 0, 1, 2, 3, and so on. Algebra I Cheat Sheet Axioms of Equality This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 7 Reflexive axiom: a = a Symmetric axiom: If a = b, then b = a Transitive axiom: If a = b and b = c, then a = c Additive axiom: If a = b and c = d, then a + c = b + d Multiplicative axiom: If a = b and c = d, then ac = bd Solving Equations 1. Simplify if necessary. 2. Get the variable on one side of the equal sign and numbers on the other. 3. Divide by the number in front of the variable. Solving Systems of Equations Addition/Subtraction Method: Combine equations to eliminate one variable. The equations may need to be multiplied by a common multiple first. Substitution Method: Solve one equation for one variable and substitute that variable into other equations. Graphing Method: Graph each equation on the same graph. The coordinates of the intersection are the solution. Monomials A monomial is an algebraic expression that consists of only one term. • Add or subtract monomials with like terms only: 3xy + 2xy = 5xy. • To multiply monomials, add the exponents of the same bases: x4(x3) = x7. • To divide monomials, subtract the exponent of the divisor from the exponent of the dividend of the same base: x8/x3 = x5. Polynomials A polynomial is an algebraic expression of two or more terms, such as x + y. Binomials consist of exactly two terms. Trinomials consist of exactly three terms. • To add or subtract polynomials, add or subtract like terms only. • To multiply two polynomials, multiply each term in one polynomial by each term in the other polynomial. The F.O.I.L. method (first, outer, inner, last) is often used when multiplying binomials. • To divide a polynomial by a monomial, divide each term by the monomial. • To divide a polynomial by another polynomial, make sure both are in descending order, then use long division (divide by first term, multiply, subtract, bring down). Solving Inequalities Solve exactly like equations, except if you multiply or divide both sides by a negative number, you must reverse the direction of the inequality sign. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 10 Ellipse Centered at (h, k) with its major axis parallel to the x-axis: Centered at (h, k) with its major axis parallel to the y-axis: Parabola If parabola opens vertically: y = a(x - h)2 + k If parabola opens horizontally: x = a(y - k)2 + h Hyperbola If transverse axis is horizontal: If transverse axis is vertical: Sequences and Series Arithmetic Sequence an = a1 + (n - 1)d Geometric Sequence an = a1 r n-1 Arithmetic Series Geometric Series Geometry Cheat Sheet ∠, ∠s Angle, angles m∠AB Measure of angle AB Arc AB Measure of arc AB Circle, circles Congruent Not congruent Degree This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 11 = Equal ≠ Not equal > Greater than < Less than AB Length of line segment AB AB Line AB Line segment AB Ray AB || Parallel Not parallel Parallelogram ∠ Perpendicular ˜ Similar ∆ Triangle (x,y) Ordered pair in plane a⁄b = c⁄d Proportion a: b or a⁄b Ratio Famous Abbreviations AA Angle-angle, for proving triangles similar AAS Angle-angle-side, for proving triangles congruent ASA Angle-side-angle, for proving triangles congruent cos Cosine cot Cotangent CPCTC Congruent parts of congruent triangles are congruent csc Cosecant CSSTP Corresponding sides of similar triangles are proportional SAS Side-angle-side, for proving triangles congruent sin Sine tan Tangent Commonly Used Variables a Apothem a, b, c Lengths of the sides of a triangle A Area of a polygon B Area of the base of a solid C Circumference of a circle h Height of an altitude α Alpha (name of an angle) This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 12 β Beta (name of an angle) X1 x Unknown value θ Theta (name of an angle) π Pi Slant length of a side of a solid l or l Length of a rectangle L Lateral area of a solid m Slope of a line M Midpoint of a line segment n Number of sides of a polygon P Perimeter of a polygon P or P' Plane r Radius s Length of the side of an equilateral polygon S Surface area of a solid T Total area V Volume w or w Width of a rectangle Formulae Area (A) of a triangle A = ½bh where b measures the base and h the altitude Perimeter (P) of a triangle P = a + b + c where a, b, and c are the lengths of the sides Area (A) of a rectangle A = lw where l measures the length and w the width Perimeter (P) of a rectangle P = 2b + 2h where b measures the width and h the height Area (A) of a circle A = πr2 where r measures the radius Area Circumference (C) of a circle C = 2πr or C = πd where r measures the radius and d the diameter Geometry Glossary A B C D E H I L M N O P Q R S T V A acute angle: an angle whose measure is less than 90°. acute triangle: a triangle containing all acute angles. adjacent angles: angles that share a common side and a common vertex. angle: formed by two rays with a common endpoint. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 15 N nonagon: a plane closed figure with nine sides and nine angles O obtuse angle: an angle greater than 90° but less than 180° obtuse triangle: a triangle containing an obtuse angle octagon: a plane closed figure with eight sides and eight angles P parallel lines: two or more lines, always the same distance apart. Parallel lines never meet. parallelogram: a four-sided plane closed figure having opposite sides equal and parallel. (Opposite angles are equal, and consecutive angles are supplementary.) pentagon: a five-sided plane closed figure. The sum of its five angles is 540°. perimeter: the total distance around the outside of any polygon. The total length of all the sides. perpendicular lines: two lines that intersect at right angles. pi (π): a constant used in determining a circle's area or circumference. Equals approximately 3.14 or 22/7 plane: often described as a flat surface. plane figure: shape having only length and width (two dimensional). plane geometry: the study of shapes and figures in two dimensions. point: a basic element of geometry, a location. If two lines intersect, they do so at a point. polygon: many-sided plane closed figure. Triangle, quadrilateral, pentagon, and so on. prism: a three-dimensional shape bounded by congruent parallel faces and a set of parallelograms formed by joining the corresponding vertices of the bases. Pythagorean theorem: a theorem that applies to right triangles. The sum of the squares of a right triangle's two legs equals the square of the hypotenuse (a2 + b2 = c2). Q quadrilateral: a four-sided plane closed figure. The sum of its four angles equals 360°. R This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 16 radii: plural of radius. radius: a line segment whose endpoints lie one at the center of a circle and one on the circle. Also, the length of this segment. ray: a half-line. Continues forever in one direction. Has one endpoint. rectangle: a four-sided plane closed figure having opposite sides equal and parallel and four right angles. regular polygon: a polygon in which sides and angles are all equal. For example, a regular pentagon has five equal angles and five equal sides. rhombus: a parallelogram with four equal sides. right angle: an angle whose measure is equal to 90°. right circular cylinder: a solid shaped like a can. Base meets side at a right angle. right triangle: a triangle containing a 90° angle. S scalene triangle: a triangle having none of its sides equal (or angles equal). similar: having the same shape but not the same size, in proportion. solid geometry: the study of shapes and figures in three dimensions: length, width, and thickness. square: a four-sided plane closed figure having equal sides and four right angles. Its opposite sides are parallel. straight angle: an angle equal to 180°. Often called a line. straight line: often described as the shortest distance between two points. Continues forever in both directions. (Line means straight line.) supplementary angles: two angles the sum of which measures 180°. surface area: the total surface of all sides of a solid, or the total area of faces. T tangent to a circle: a line, line segment, or ray that touches a circle at one point (cannot go within the circle). transversal: a line crossing two or more parallel or nonparallel lines in a plane. trapezoid: a four-sided plane closed figure with only one pair of parallel sides, called bases. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 17 triangle: a three-sided plane closed figure. Contains three angles the sum of whose measures is 180°. V vertex: the point at which two rays meet and form an angle, or the point at which two sides meet in a polygon. vertical angles: the opposite angles formed by the intersection of two lines. Vertical angles are equal in measure. vertices: plural of vertex. volume: capacity to hold, measured in cubic units. Volume of rectangular prism = length x width x height. Trigonometry Glossary A B C D E G H I L M N O P Q R S T U V Z A AAS: reference to solving a triangle given the measure of two angles and the length of a non- included side. absolute value of a complex number: square root of the sum of the squares of its real and imaginary coefficients. algebraic vector: an ordered pair of numbers representing the terminal point of a standard vector. amplitude of a complex number: same as the argument of a complex number. amplitude: the vertical stretch of a function. angle: a measure of rotation. angle of depression: an angle measured below the horizontal. angle of elevation: an angle measured above the horizontal. angular velocity: defined in terms of angle of rotation and time. argument of a complex number: angle formed between the positive x-axis and a line segment between the origin and the number. ASA: reference to solving a triangle given the measure of two angles and the length of the included side. ASTC: an acronym representing which trigonometric functions are positive in the I, II, III, and IV quadrants respectively. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 20 inverse cosine function: inverse of the restricted cosine function. inverse cotangent function: defined in terms of the restricted tangent function. inverse notation: notation used to express an angle in terms of the value of trigonometric functions. inverse secant function: defined in terms of the restricted cosine function. inverse sine function: inverse of the restricted sine function. inverse tangent function: inverse of the restricted tangent function. L law of cosines: a relationship between the lengths of the three sides of a triangle and the cosine of one of the angles. law of sines: a relationship between the ratios of the sines of angles of a triangle and the side opposite those angles. linear interpolation: a method of approximating values in a table using adjacent table values. linear velocity: defined in terms of arc length and time. M magnitude of a vector: the length of the directional line segment. mathematical induction: a method of mathematical proof. maximum value: largest value of a function in a given interval. minimum value: smallest value of a function in a given interval. minute: an angle measurement equal to 1/60 of a degree. modulus of a complex number: same as absolute value of a complex number. N negative angle: results from clockwise rotation. norm: another name for the magnitude of a vector. nth root theorem: an extension of De Moivre's theorem involving roots of complex numbers. O This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 21 odd function: a function is odd of f(-x) = -f(x). odd-even identities: fundamental identities that involve the basic trig functions of negative angles. Also called identities for negatives. one-to-one: a characteristic of functions where each element in the domain is pairs with one and only one element in the range and vice versa. orthogonal: perpendicular. P parallelogram rule: a process used to add together two nonparallel vectors. period: the smallest value of q such that f(x) = f(x+q) where f(x) is a periodic function. periodic functions: trigonometric functions whose values repeat once each period. phase shift: the horizontal displacement of a function to the right or left of the vertical axis. polar axis: a ray extending from the pole in a polar coordinate system. polar coordinate system: a coordinate system using distance and angle for position. polar coordinates: an ordered pair consisting of a radius and an angle. pole: the fixed center of the polar coordinate system. position vector: another name for a standard vector. positive angle: results from counterclockwise rotation. primary solutions: solutions defined over a limited domain. principal nth root: the unary root of a complex number. product-sum identities: useful in writing the product of trig functions as the sum and difference of trig functions. projections: another name for component vectors, the horizontal and vertical component vectors of a given vector. proving the identity: showing the validity of one identity by using previously known facts. Pythagorean identities: fundamental identities that relate the sine and cosine functions and the Pythagorean Theorem. Q quadrantal angle: an angle in standard position with its terminal side on a coordinate axis. quotient identities: fundamental identities that involve the quotient of basic trig functions. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 22 R radian: the measure on an angle with vertex at the center of a circle that subtends an arc equal to the radius of the circle. radius vector: another name for a standard vector, a vector in standard position. real axis: an axis in the complex plane. reciprocal identities: fundamental identities that involve the reciprocals of basic trig functions. reduction formulas for cosine: useful in rewriting cosines of angles greater than 90° as functions of acute angles. reduction formulas for sine: useful in rewriting sines of angles greater than 90° as functions of acute angles. reduction formulas for tangent: useful in rewriting tangents greater than 90° as functions of acute angles. reference angle: an acute angle whose trigonometric ratios are the same (except for sign) as the given angle. resultant vector: the result obtained after vector manipulation. S SAS: reference to solving a triangle given the lengths of two sides and the measure of the included angle. scalar multiplication: changing the magnitude of a vector without changing its direction. scalar multiplication of algebraic vectors: a processes of multiplying vector components. scalar quantity: the value of a dot product of two vectors. secant: the reciprocal of the cosine function. second: an angle measurement equal to 1/60 of a minute. sector: a portion of a circle enclosed by a central angle and its subtended arc. semiperimeter: one-half the perimeter of a triangle. similar triangles: two triangles whose angle measurements are the same. simple harmonic motion: a component of uniform circular motion. sine: a trigonometric ratio equal to the opposite side divided by the hypotenuse. solving the triangle: a process for finding the values of sides and angles of a triangle given This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 25 This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 26 Trigonometry Table This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 27 Derivative Table This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 30 15. 16. 17. 18. 19. 20. Statistics Glossary A B C D E F G H I J L M N O P Q R S T U V Z A addition rule: for mutually exclusive random events, the chance of at least one of them occurring is the sum of their individual probabilities. alternative hypothesis: a research hypothesis; the hypothesis that is supported if the null hypothesis is rejected. B bar chart: a graphic that displays how data fall into different categories or groups. bell-shaped curve: symmetrical, single-peaked frequency distribution. Also called the normal curve or gaussian curve. bias: the consistent underestimation or overestimation of a true value, because of preconceived notion of the person sampling the population. bimodal: curve with two equal scores of highest frequency. binomial: event with only two possible outcomes. binomial probability distribution: for binomial events, the frequency of the number of favorable outcomes. For a large number of trials, the binomial distribution approaches the normal distribution. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 31 bivariate: involving two variables, especially, when attempting to show a correlation between two variables, the analysis is said to be bivariate. box plot (box-and-whiskers): a graphic display of data indicating symmetry and central tendency. C Central Limit Theorem: a rule that states that the sampling distribution of means from any population will be normal for large sample n. chi-square: a probability distribution used to test the independence of two nominal variables. class frequency: the number of observations that fall into each class interval. class intervals: categories or groups contained in frequency graphics. coefficient of determination: a measure of the proportion of each other's variability that two variables share. confidence interval: the range of values that a population parameter could take at a given level of significance. confidence level: the probability of obtaining a given result by chance. continuous variable: a variable that can be measured with whole numbers and fractional (or decimal) parts thereof. correlated: two (or more) quantities that change together in a consistent manner. Thus, if the value of one variable is known, the other can be immediately determined from their relationship. correlation coefficient: a measure of the degree to which two variables are linearly related. critical value: the value of a computed statistic used as a threshold to decide whether the null hypothesis will be rejected. D data: numerical information about variables; the measurements or observations to be analyzed with statistical methods. degrees of freedom: a parameter used to help select the critical value in some probability distributions. dependent events: events such that the outcome of one has an effect on the probability of the outcome of the other. dependent variable: a variable that is caused or influenced by another. descriptive statistics: numerical data that describe phenomena. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 32 deviation: the distance of a value in a population (or sample) from the mean value of the population (or sample). directional test: a test of the prediction that one value is higher than another; also called a one-tailed test. discrete variable: a variable that can be measured only by means of whole numbers; or one which assumes only a certain set of definite values, and no others. disjoint occurrence: both outcomes unable to happen at the same time. distribution: a collection of measurements; how scores tend to be dispersed about a measurement scale. dot plot: a graphic that displays the variability in a small set of measures. double counting: a mistake encountered in calculating the probability of at least one of several events occurring, when the events are not mutually exclusive. In this case, the addition rule does not apply. E empirical rule: a rule that is founded on observation, without a theoretical basis. Or a "rule of thumb." F frequency distribution: the frequency of occurrence of the values of a variable. For each possible value of the variable, there is an associated frequency with which the variable assumes that value. frequency histogram: a graphic that displays how many measures fall into different classes, giving the frequency at which each category is seen observed. frequency polygon: a graphic presentation of frequency of a phenomenon that typically uses straight lines and points. G grouped data: data that has been sorted into categories, usually in order to construct a frequency histogram. grouped measures: a set of values that belong to the same class. H histogram: a graphic presentation of frequency of a phenomenon. I This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 35 divided appropriately. point estimate: a number computed from a sample to represent a population parameter. population: a group of phenomena that have something in common. The population is the larger group, whose properties (parameters) are estimated by taking a smaller sample from within the population, and applying statistical analysis to the sample. positive relationship: a relationship between two variables such that when one increases, the other increases, or when one decreases, the other decreases. positively skewed curve: a probability or frequency distribution that is not normal, but rather is shifted such that the mean is greater than the mode. power: the probability that a test will reject the null hypothesis when it is, in fact, false. probability: a quantitative measure of the chances for a particular outcome or outcomes. probability distribution: a smooth curve indicating the frequency distribution for a continuous random variable. proportion: for a binomial random event, the probability of a successful (or favorable) outcome in a single trial. Q qualitative variable: phenomenon measured in kind, that is, non-numerical units. For example, color is a qualitative variable, because it cannot be expressed simply as a number. quantitative variable: phenomenon measured in amounts, that is, numerical units. For example, length is a quantitative variable. R random: an event for which there is no way to know, before it occurs, what the outcome will be. Instead, only the probabilities of each possible outcome can be stated. random error: error that occurs as a result of sampling variability, through no direct fault of the sampler. It is a reflection of the fact that the sample is smaller than the population; for larger samples, the random error is smaller. range: difference between the largest and smallest measures of a set. ratio: a scale using numbers to rank order; its intervals are equal, and the scale has an absolute 0 point. region of acceptance: the area of a probability curve in which a computed test statistic will lead to acceptance of the null hypothesis. region of rejection: the area of a probability curve in which a computed test statistic will lead to rejection of the null hypothesis. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 36 regression: a statistical procedure used to estimate the linear dependence of one or more independent variables on a dependent variable. relative frequency: the ratio of class frequency to total number of measures. relative frequency principle of probability: if a random event is repeated a large number of times, then the proportion of times that a particular outcome occurs is the probability of that outcome occurring in a single event. research hypothesis: a prediction or expectation to be tested. If the null hypothesis is rejected, then the research hypothesis (also called alternative hypothesis) is supported. residual: the vertical distance between a predicted value y and its actual value. S sample: a group of members of a population selected to represent that population. A sample to which statistical analysis is applied should be randomly drawn from the population, to avoid bias. sampling distribution: the distribution obtained by computing a statistic for a large number of samples drawn from the same population. sampling variability: the tendency of the same statistic computed from a number of random samples drawn from the same population to differ. scatter plot: a graphic display used to illustrate degree of correlation between two variables. skewed: a distribution displaced at one end of the scale and a tail strung out at the other end. slope: a measure of a line's slant. standard deviation: a measure of data variation; the square root of the variance. standard error: a measure of the random variability of a statistic, such as the mean (i.e., standard error of the mean). The standard error of the mean is equal to the standard deviation divided by the square root of the sample size (n). standardize: to convert to a z-score. statistic: a characteristic of a sample. A statistic is an estimate of a population parameter. For larger samples, the statistic is a better estimate of the parameter. statistical significance: the probability of obtaining a given result by chance. High statistical significance does not necessarily imply importance. statistics: a branch of mathematics that describes and reasons from numerical observations; or descriptive measures of a sample. stem-and-leaf graphic: display that shows actual scores as well as distribution of classes. symmetry: a shape such that one side is the exact mirror image of the other. This file has been downloaded from OneStopGRE.com. For more GRE Preparation Stuff, Alerts and other details, visit http://www.onestopgre.com. GRE related discussions, visit http://forum. onestopgre.com . Visit http://groups.yahoo.com/group/onestopgre / for joining the club of GRE Aspirants 37 symmetric distribution: a probability or frequency distribution that has the property in which the mean, median, and mode are all the same value. systematic error: the consistent underestimation or overestimation of a true value, due to poor sampling technique. T t-distribution: a probability distribution often used when the population standard deviation is not known or when the sample size is small. tabled value: the value of a computed statistic used as a threshold to decide whether the null hypothesis will be rejected. test statistic: a computed quantity used to decide hypothesis tests. two-tailed test: a test of the prediction that two values are equal, or a test that they are not equal. Type I error: rejecting a null hypothesis that is, in fact, true. Type II error: failing to reject a null hypothesis that is, in fact, false. U upper quartile: (Q3), the 75th percentile of a set of measures. V value: a measurement or classification of a variable. variable: an observable characteristic of a phenomenon that can be measured or classified. variance: a measure of data variation; the mean of the squared deviation scores about the means of a distribution. Z z-score: a unit of measurement obtained by subtracting the mean and dividing by the standard deviation. Courtesy: Cliff Notes.