Download Statistics in Psychology: Descriptive, Inferential, and Graphical Techniques and more Slides Cognitive Psychology in PDF only on Docsity! Behavioral Statistics Docsity.com Types of Statistics in Psychology Descriptive Statistics: Summarize numbers so they become more meaningful and easier to communicate to other people Inferential Statistics: Used for making decisions, for generalizing from small samples, and for drawing conclusions Docsity.com Fig. A.2 Frequency polygon of hypnotic susceptibility scores contained in Table A.2. Docsity.com Measures of Central Tendency A number that describes a typical score around which the other scores fall Mean: Add all the scores for each group and then divide by the total number of scores; one type of average Sensitive to extremely high or low scores in a distribution; not always the best measure of central tendency Docsity.com Measures of Central Tendency (cont.) Median: Arrange scores from highest to lowest and then select the score that falls in the middle; half the values fall above the median, and half fall below it Mode: Identifies the most frequently occurring score in a group Easy to obtain but often unreliable Main advantage: Gives the score actually obtained by the most people Docsity.com Fig. A.3 The normal curve. The normal curve is an idealized mathematical model. However, many measurements in psychology closely approximate a normal curve. The scales you see here show the relationship of standard deviations, z-scores, and other measures to the curve. Docsity.com Fig. A.4 Relationship between the standard deviation and the normal curve. Docsity.com Inferential Statistics Population: Entire set of subjects, objects, or events of interest (all married students in the United States) Impossible or impractical to obtain Samples: Smaller cross section of a population Easier and more practical (and cheaper!) to obtain More cost effective Docsity.com Correlation (cont.) Zero Correlation: No relationship exists between two variables Relationship between hair color and intelligence test scores (IQs) Negative Relationship (or Correlation): As values of one measure increase (X), values in the other measure decrease (Y) The more alcohol you drink, the lower your coordination test scores will be Docsity.com Fig. A.5 Scatter diagrams showing various degrees of relationship for a positive, zero, and negative correlation. (Adapted from Pagano, 1981.) Docsity.com Coefficient of Correlation Statistical index ranging from –1.00 to +1.00; the sign indicates the direction of the relationship, and the number, the strength Perfect Positive Relationship: Correlation of +1.00 Perfect Negative Relationship: Correlation of – 1.00 Perfect correlations are rarely found in psychology It is statistically impossible to have a correlation coefficient greater than +1.00 or lesser than –1.00 Percent of Variance: Amount of variation in scores accounted for by the correlation Docsity.com
