any examination in which two or more quantities are compared after data have been collected and without prior plans to carry out the particular comparison. For example, after obtaining a significant F ratio for a data set, a researcher may perform post hoc comparisons to follow up on and help explain the initial findings. Different statistical tests are required for post hoc comparisons than for a priori comparisons. Also called a posteriori comparison (or contrast); post hoc contrast; unplanned comparison (or contrast).