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bivariate correlation
an association that involves exactly two variables
effect size
the strength of a relationship between two more more variables
statistically significant
a correlation that is unlikely to have come from a population in which the association is zero
restriction of range
this can occur if there is not a full range of scores on one of the variables in the association, so the correlation appears smaller than it really is
curvilinear relationship
a relationship between two variables that is not a straight line
the directionality problem
states the method must ensure that the cause variable preceded the effect variable
the third-variable problem
states that there must be no plausible alternative explanation for the relationship between the two variables
spurious relationship
the bivariate correlation is there, but only because of some third variable
moderator
when the relationship between two variables changes depending on the level of another variable, the other variable is called this