PSY 290A Lecture Notes - Lecture 17: Causal Inference, Categorical Variable, Scatter Plot
11 Dec 2016
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Document Summary
Correlational studies can include both quantitative and categorical variables (but they are graphed differently) If the correlation is 0, it might be curvilinear. It can make the correlation appear smaller than it really is. Apply covariance (is there an association), temporal precedence (does one come before the other), internal validity (are there any alternative explanations) Directionality problem - a situation in which it is unclear which variable in an association came first. Third-variable problem - a situation in which a plausible alternative explanation exists 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. External validity: moderators address external validity, moderators - a variable that, depending on its level, changes the relationship between two other variables, moderators and external validity.
