Correlation Regression

quantitative or categorical

The variables in a bivariate correlational study can be either

scatterplot

If both variables are quantitative, the data are usually depicted in a

bar graph

if one variable is categorical, the data are usually depicted in a

scatterplot

For a —, the correlation coefficient r can be used to describe the relationship.

bar graph

For a —, the difference between the two group means is used to describe the relationship.

construct validity

Because a correlational study involves two measured variables, the — of each measure must be interrogated in a bivariate correlation study.

effect size (strength of r)

precision (confidence interval of r)

replication of the study

the presence of outliers

possible restriction of range

and whether the association is curvilinear.

Interrogating the statistical validity of an association claim involves six areas of inquiry:

Internal validity

addresses the degree to which a study supports a causal claim.

moderated

A bivariate correlation is sometimes —, which means the relationship changes depending on the levels of another variable, such as gender, age, or location.

bivariate association

An association that involves exactly two variables, also called —

Effect size

is the magnitude, or strength, of a relationship between two or more variables.

Replication

is the process of conducting a study again to test whether the result is consistent.

Outlier

is a score that stands out as either much higher or much lower than most of the other scores in a sample.

Restriction of range

In a bivariate correlation, the absence of a full range of possible scores on one of the variables, so the relationship from the sample underestimates the true correlation.

Curvilinear Association

An association between two variables which is not a straight line; instead, as one variable increases, the level of the other variable increases and then decreases (or vice versa).

Directionality Problem

In a correlational study, the occurrence of both variables being measured around the same time, making it unclear which variable in the association came first.

Third-variable Problem

In a correlational study, the existence of a plausible alternative explanation for the association between two variables.

Moderator

A variable that, depending on its level, changes the relationship between two other variables

Regression Analysis

A tool that enables us to predict an individual’s score on one variable based on knowing other variables

Regression Equation

Regression Analysis allows making predictions by developing a

Regression Line

is the best fitting line drawn thru the center of the scatterplot that indicates the relationship between the variables

Multiple Regression (MR)

A more advanced use of regression analysis, involves combining several predictor variables in a single regression equatio

Interaction

In real world, it is unlikely that one variable is affected by only one variable