# PSYC 3500 Study Guide - Quiz Guide: Univariate Distribution, Dependent And Independent Variables, Joint Probability Distribution

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PSY 3500: Correlation & Regression

Study Guide

1

• Univariate distribution - We focus on one variable in time.

• Bivariate distribution - Statistics related to the relationship between two variables.

• Correlation - A statistic that times whether not to distribution/variables are related;

specifies the nature ( + or -) or degree of the relationship.

• Requires pairs of the scores for each participant.

• Regression - A process in which we can predict values of one variable from values of

another variable; takes a correlation one step further by adding in a line of best fit.

• Range of r - -1 - +1

• If r is a positive number - You have a positive correlation.

• As one variable increases the other variable increases.

• If r is a negative number - You have a negative correlation.

• As one of able decreases the other variable decreases.

• If r equals zero - We have no linear relationship between two variables.

• Scatterplot - How we graph scores of bivariate frequency distributions.

• Interpreting r - The larger the absolute value of r the larger the correlation

• Weak - r=.10

• Medium / moderate - r=.30

• Large / strong - r=.50

• Lower third - r<.20

• Middle third - r=.20 - .30

• Upper third - r>.30

• What does r not tell us? - R does not imply a percent of association

• R=.8 is not two times the effect of an r=.4

• Why are correlations useful? - Prediction