psych 225 exam - second run

bivariate correlation

An association that involves exactly two variables. Also called bivariate association.

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

n 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). See also negative association, positive association, zero association.

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. See also temporal precedence.

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. See also internal validity.

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.