Research methods and statistics are core courses in the undergraduate psychology major. To assess learning outcomes, it would be useful to have a measure that assesses research methods and statistical literacy beyond course grades. In two studies, we developed and provided initial validation results for a research methods and statistical knowledge…

Yule (1903) and Simpson (1951) described a statistical paradox that occurs when data is aggregated. In such situations, aggregated data may reveal a trend that directly contrasts those of sub-groups trends. In fact, the aggregate data trends may even be opposite in direction of sub-group trends. To reveal Yule-Simpson's paradox (YSP)-type…

Regardless of the related discipline, students in statistics courses invariably have difficulty understanding the connection between the numerical values calculated for end-of-the-chapter exercises and their usefulness in decision making. This disconnect is, in part, due to the lack of time and opportunity to actually design the experiments and…

Georg Rasch has developed a new one-parameter latent trait model to explain the performance of examinees on achievement tests. The model can be viewed as a special case of Birnbaum's two-parameter logistic model where all items are assumed to have equal discriminating power. Birnbaum's model permits items to vary in discriminating power. Both…

A visual display is introduced that enables one to compare the predictive validities of all possible non-negatively weighted sums of two predictors. This two-predictor validity curve assesses the level of predictability of a criterion from composites of two predictors. Derivations are presented for the general case. For illustrative purposes, the…