a priori comparison
any examination in which two or more quantities are compared in accordance with plans established prior to conducting a research study. For example, even before data are collected, a researcher might hypothesize that two groups given personal instruction would show better mean performance on a task compared to those who receive only written instruction. Thus, he or she could decide in advance to compare the combined personal instruction groups to the written instruction groups. Also called a priori contrast; planned comparison (or contrast).