Ch. 8 Definitions: Bivariate Correlational Research

Bivariate correlation

An association that involves exactly two variables

Mean

An arithmethic average; a measure of central tendency computed from the sum of all the scores in a set of data, divided by the total number of scores

Effect size

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

Statistically significant

In NHST, the conclusion assigned when when p < .05; that is, when it is unlikely the result came from the null hypothesis population.

Replication 

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

Outlier

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 that 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

Reverse causation

In a study that finds a relationship between variables A and B, the plausible inference that either A could cause B or that B could cause A.

Third-variable problem 

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

Spurious association

A bivariate association that is attributable only to systematic mean differences on subgroups within the sample; the original association is not present within the subgroups.

Moderator

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