Statistics in Psychology: Midterm Review, Exams of Psychology

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Statistics in Psychology Midterm cases - the participants in or subjects of a study cofounding variable - a third variable in correlational and quasi-experimental designs that is not controlled for and that has an impact on both of the other variables correlational design - a scientific study in which the relationship between two variables is examined without any attempt to manipulate or control them criterion variable - the outcome variable in a correlational design dependent variable - the variable where the effect is measured in an experimental or quasi-experimental study descriptive statistic - a summary statement about a set of cases experimental design - a scientific study in which an explanatory variable is manipulated or controlled by the experimenter and the effect is measured in a dependent variable explanatory variable - the variable that causes, predicts or explains the outcome variable grouping variable - the variable that is the explanatory variable in a quasi-experimental design independent variable - the variable that is controlled by the experimenter in an experimental design inferential statistic - using observations from a sample to draw a conclusion about a population interval-level numbers - numbers that provide information about how much of an attribute is possessed, as well as information about same/different and more/less; have equality of units and an arbitrary zero point nominal-level numbers - numbers used to place cases in categories; numbers are arbitrary and only provide information about same/different ordinal-level numbers - numbers used to indicate if more or less of an attribute is possessed; numbers provide information about same/different and more/less outcome variable - the variable that is caused, predicted or influenced by the explanatory variable parameter - a value that summarizes a population population - the larger group of cases a researcher is interested in studying Which of the following would make it difficult to determine if our independent variable truly had an effect on the dependent variable? - the presence of a confounding variable If we were interested in studying the effect of drug abuse on employment, we could not use a(n) _____ design because of ethical issues involved in employing random assignment. - experimental Dr. Ramirez wants to compare the effects of a new treatment for multiple sclerosis (MS) in patients in early stages of the disease to the effects in patients with advanced MS. She decides a quasi- experimental design is best for her study. Why? - She cannot use an experimental design because patients cannot be randomly assigned. I decide to use the identifier 1 for a woman and 2 for a man in my study. Using numbers to simply identify or label these categories involves _____ variables. - nominal-level A difference between an interval variable and a ratio variable is that an interval variable - does not have a true zero point Measuring a person's weight in pounds would involve using a(n) _____ variable. - ratio-level If a market research company studies the television viewing habits of 1,000 randomly selected families and uses the information to make inferences about the viewing habits of all families in the United States, it is utilizing: - inferential statistics In statistical notation, the symbol N represents the - number of cases In statistical notation, Ex means - to add together all the scores. What is the first step in the following problem: (6 + 2)² ÷ 12 x 3? - add 6 and 2 Suppose that students are randomly assigned to get either positive feedback or other feedback for their performance on daily quizzes, and we measure their attitudes toward the class at the end of the semester. What is the independent variable in this study? - to get positive feedback or other feedback The variable that is measured to determine if the independent variable had an effect is referred to as the _____ variable. - dependent A researcher wants to know if mood affects productivity at work. The explanatory variable is - participant mood The number of goals scored in a soccer game is an example of a(n) _____ variable. - ratio-level Which branch of statistics uses numerical observations and incorporates them into an organized and informative summary of the data? - descriptive Two basic branches of statistics are _____ and _____. - descriptive; inferential CH.2: apparent limits - what seems to be the upper and lower bounds of an interval in a grouped frequency distribution bar graph - a graph of a frequency distribution for discrete data that uses the heights of bars to indicate frequency; the bars do not touch countinuous numbers - answer the question "how much" and can have in-between values; the specificity of the number, the number of decimal places reported, depends on the precision of the measuring instrument cumulative frequency - a count of how often a given value, or a lower value, occurs in a set of data cumulative percentage - cumulative frequency expressed as a percentage of the number of cases in the data set discrete numbers - answer the question "how many," take whole number values, and have no in-between values frequency distribution - a tally of how often different values of a variable occur in a set of data frequency polygon - a frequency distribution for continuous data, displayed in graphical format, using a line connecting dots, above interval midpoints, that indicate frequency grouped frequency distribution - a count of how often the values of a variable, grouped into intervals, occur in a set of data X = the distance a car could be driven with only 1 gallon of gas. - continuous Megan is a researcher studying memory in older adults. For one variable "memory," she has organized her participants' scores into a frequency distribution and wants to graph the results. Which of these could Megan use? - histogram A total of 300 people were asked the following question: How many times have you accessed the Internet this week? - none - once or twice - three or four times - more than four times Which is the BEST method of displaying the data produced from that question? - bar graph Creating a(n) _____ distribution involves summarizing a group of data by listing each possible value along with how frequently the value occurred. - ungrouped frequency Imagine that you have collected eye-color data for 500 people. Would you present an ungrouped frequency distribution table or a grouped frequency distribution table? - ungrouped, because the number of possible eye colors is limited Which of the following represents the correct way to form intervals for a grouped frequency table? - Dr. C groups her data into 5 intervals with ranges 1-9.99, 10-19.99, and so on. The U.S. Census asks participants to indicate the number of children in their household. What type of data are these? - discrete Which type of variable could theoretically include an infinite number of possible values between any two consecutive numbers? - continuous For a continuous variable represented in a grouped frequency distribution, the _____ limits of an interval are the true limits, which typically fall outside of the upper and lower bounds listed on the axis. - real A bar graph is used with _____ data, while a histogram is used with _____ data. - discrete, continuous Imagine a researcher found that 70% of bystanders helped a female who couldn't start her car but only 10% helped a male who couldn't start his car. What type of graph would be appropriate to display this data? - bar graph Identify the shape of the distribution of the following scores: 16, 15, 92, 15, 20, 25, 95, 20, 25, 20, 24, 21. - positively skewed If a distribution is positively skewed, most of the scores occur _____ of the distribution. - on the left side Dr. Kelley graphs her data and reports that her distribution is flat. Her report is highlighting which aspect of the distribution's shape? - kurtosis CH.3: central tendency - a value used to summarize a set of scores; also known as the average deviation score - a measure of how far a score falls from the mean, calculated by subtracting the mean from the score interquartile range - a measure of variability for interval- or ratio-level data; the distance covered by the middle 50% of scores; abbreviated IQR mean - an average calculated for interval or ratio-level data by summing all the values in a data set and dividing by the number of cases; abbreviated M. median - an average calculated by finding the score associated with the middle case, the case that seperates the top half of scores from the bottom half; abbreviated Mdn; can be calculated for ordinal-, interval-, or ratio-level data mode - the score that occurs with the greatest frequency outlier - an extreme (unusual) score that falls far away from the rest of the scores in a set of data range - a measure of variability for interval- or ratio-level data; the distance from the lowest score to the highest score standard deviation - a measure of variability for interval- or ratio-level data; the square root of the variance; a measure of the average distance that scores fall from the mean It is easy to spot the mode on a frequency distribution, as the most frequently occurring score is always the _____ of the distribution. - highest point _____ is the square root of the average of the squared deviations from the mean. - standard deviation CH.4: common zone - the section of a distribution where scores usually fall; commonly set to be the middle 95% extreme percentage - percentage of the normal distribution that is found in the two tails and is evenly divided between them independence - in probability, when the occurrence of one outcome does not have any impact on the occurrence of a second outcome middle percentage - percentage of the normal distribution found around the midpoint, evenly divided into two parts, one just above the mean and one just below it normal distribution - also called the normal curve; a specific ball-shaped curve defined by the percentage of cases that fall in specific areas under the curve percentile rank - percentage of cases with scores at or below a given level in a frequency distribution probability - how unlikely an outcome is; the number of ways a specific outcome can occur, divided by the total number of possible outcomes rare zone - section of a distribution where scores do not usually fall; in most instances, set to be the extreme 5% standard score - raw score expressed in terms of how many standard deviations it falls away from the mean; also known as a z-score z-score - raw score expressed in terms of how many standard deviations it falls away from the mean; also known as a standard score A raw score with a percentile rank of 63 in a distribution of scores must have a: - z score between 0 and 1.00. An individual raw score that is expressed in terms of the number of standard deviations from the mean is called a: - standard score Which of the following percentages corresponds roughly to the area beneath the standard normal curve from a z score of -1.00 to +1.00? - 68% In a normal distribution, _____% of the scores falls below the mean. - 50 The midpoint of the distribution will always fall at the _____ percentile. - 50th In statistical terms, a value that falls in the common zone would: - fall in the middle of the normal distribution. If a z score of ±1.96 marks off the middle section in a distribution, a z score of -1.25 would be considered: - in the common zone Which of the following is not a characteristic of the normal distribution? - There are two modes, or most frequently occurring scores. To determine a person's percentile rank, you first need to convert that person's raw score to a: - z-score In a standardized z distribution, the percentile rank associated with z = 0 is _____%. - 50 In a normal distribution, the score that separates the highest 10% from the rest of the scores is called the _____ percentile. - 90th The fact that a coin can land only on heads or tails, and not both, makes the outcome of coin tosses: - mutually exclusive One advantage of calculating standard scores is that we: - can compare scores that are measured on different scales The fact that each flip of a coin has no impact on the outcome of another coin flip makes the outcome of coin tosses: - As sample size increases, the shape of the sampling distribution of the mean: - becomes narrower The variability of a distribution of means is symbolized by _____, but the variability of a distribution of scores is symbolized by _____. - óm; ó A point estimate is: - one number that is used to estimate a population parameter Which of the following values is not needed in calculating the 95% confidence interval? - population mean In a set of clinical trials, a pharmaceutical company wishes to assess the effectiveness of its newly developed drug for anxiety by comparing its performance with a placebo control. In this case, is random selection appropriate? - No. There are ethical issues that keep a researcher from randomly selecting people from the population to take an experimental medication. Even with random sampling, a sample will not be representative if it: - is too small How does the sampling distribution of means for a sample with N = 5 differ from that of a sample with N = 100? - There is more variance in the sampling distribution of the mean with N = 5 than with N = 100. The mean of the sampling distribution of the mean: - is the same as the population mean of the individual scores. As sample size increases, the standard error: - decreases The cutoff z scores for the lower and upper ends of the 95% confidence interval: - are always the same As part of an assignment in a research methods class, a group of psychology students devised a survey to assess the relationship between sleep and health. Each member of the group administered the survey to five friends, and the data were then pooled. What method of sampling was used? - convenience The range of raw scores contained in an 85% confidence interval will be _____ the range of raw scores contained in a 95% confidence interval. - smaller than _____ sampling is most likely to lead to a representative sample. - random Which of the following results from random factors and is not within the control of the researcher or participant? - sampling error The measure of variability used in the formula for a confidence interval is: - standard error CH.6: hypothesis - a proposed explanation for observed facts; a statement or prediction about a population value hypothesis testing - a statistical procedure in which data from a sample are used to evaluate a hypothesis about a population nonrobust assumption - an assumption for a statistical test that must be met in order to proceed with the test null hypothesis - abbreviated Ho; a statement that in the population the explanatory variable has no impact on the outcome variable one-tailed hypothesis test - hypothesis that predicts the explanatory variable has an impact on the outcome variable in a specific direction p value - the probability of Type 1 error; the same as alpha level or significance level power - the probability of rejecting the null hypothesis when the null hypothesis should be rejected rare zone - the section of sampling distribution of a test statistic in which it is unlikely an observed outcome will fall if the null hypothesis is true; typically, 5% of the sampling distribution robust assumption - an assumption for a statistical test that can be violated to some degree and it is still OK to proceed with the test significance level - the probability of Type 1 error; the same as alpha level or p value If Bill, a researcher, fails to reject the null hypothesis when the null hypothesis is false, he has: - made a Type II error A bias toward publishing research studies that have rejected the null hypothesis implies that: - it is more likely that a published study would contain a Type I error than a Type II error. Another name for a significance level is a(n): - alpha level A Type I error occurs whenever a(n): - correct null hypothesis is rejected A social psychologist is interested in learning whether lowering a person's self-esteem increases his or her level of aggression. All of her participants complete a difficult math exam, and some of them are given inaccurate, negative results (e.g., "you missed all of the questions," or "this is the lowest score I've ever seen") that are designed to lower their self-esteem. Other participants do not receive the negative feedback. Later on, all the participants are given the opportunity to shock another person (presumably as part of a different study). Imagine that the researcher in this example made a Type I error. What could this mean? - The researcher said that low self-esteem causes increased aggression, but, in actuality, it does not. If the value of beta is 0.25, then the power is: - 0.75 The _____ hypothesis assumes that there is a difference between populations. - alternative Which of the following is not a step of hypothesis testing? - assume the alternative hypothesis is true If we reject the null hypothesis, our result is said to be: - statistically significant Imagine that you randomly select a sample of 30 newborn infants and find that their mean weight is 8.1 pounds. The population mean of newborn infants is known to be 7.4 pounds with a standard deviation of 1.1 pounds. What value would allow you to compare the mean of this sample to the mean of the population? - z statistic A fellow student failed to replicate the conformity effect, a well-established and repeatedly demonstrated effect in social psychology. Because this student failed to find a statistically significant difference in conformity when the confederates or actors gave incorrect responses, it is possible that the student: - made a Type II error In hypothesis testing, we make statements about _____ not _____. - populations; samples The null hypothesis for a z test states that: - the sample you are studying is not different from the population from which it was drawn A researcher tests the effects of playing action video games on the spatial cognitive skills in the elderly. The researcher decides to use a one-tailed hypothesis. What does this mean? - The researcher will predict that the video games will either improve or impair spatial cognition but not both The symbol for the null hypothesis is _____, and the symbol for the alternative hypothesis is _____. - Ho; H1