Читать книгу The Research Experience - Ann Sloan Devlin - Страница 137

Differential selection (biased selection of subjects) is a problem when preexisting characteristics of participants may affect scores on the dependent variable. Imagine we were interested in the effect of exposure to nature on mood, and we unknowingly selected students raised in urban areas, all of whom had been placed in one residence hall where first-year students were recruited for the study. In this kind of situation, their upbringing cannot be separated from exposure to our intervention (e.g., a camping experience in the woods). To avoid this situation, we might do a preevaluation of demographic characteristics (type of upbringing) to avoid this lopsidedness and then randomly distribute students with different kinds of upbringing across our conditions.