A variety of statistical procedures exist. The appropriate statistical procedure depends on the research question(s) we are asking and the type of data we collected.
"independent variable" with variables that are manipulated rather than observed, or known rather than predicted, or measured earlier in time rather than later (if we predict high school grades from college grades, which variable is "independent?"), or are categorical rather than continuous, or are thought of as causes rather than effects. I explain that the use of the terms "independent variable" and "dependent variable" in nonexperimental research can cause confusion, but confess to doing it myself (but I am trying to stop this bad habit). I suggest alternative terms such as "predictor variable," "factor," (in ANOVA, but the American Psychological Association does not like that use), "grouping variable," "classification variable," "criterion variable," "outcome variable," and "response variable."
- Use the terms "independent variable" and "dependent variable" only with experimental research. With nonexperimental research use "predictor variable" and "criterion variable."
- "Independent variables" temporally precede "dependent variables."
- The "independent variable" is the one that you think of as causal, the "dependent variable" is the one that you think of as being affected by the "independent variable."
- It is helpful to distinguish between "manipulated independent variables" and "measured independent variables."
- At some point in the class, it may be helpful to get out all of the various terms used to describe research variables (such as independent variable, explanatory variable, predictor, regressor, covariate, concomitant variable, nuisance variable, control variable, dependent variable, response variable, criterion, etc.) and discuss them.
- The way the terms "independent variable" and "dependent variable" are used these days causes much confusion and some mischief.
- Being fastidious about mere vocabulary is unlikely to help. Even the most fastidious experimental psychologists' views of what does, in fact, warrant causal inference is so naive and outdated as to not really be worth defending so vigorously.
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