Blessing is conducting an experiment on how children respond to different types of math problems. She gives some children problems with pictures and other children problems without pictures, and she plans to measure which group gets more problems right. Blessing wants to be certain that her manipulation of the types of problems is clear and is the cause of any differences between the groups. She also wants to ensure that her statistical conclusions will be accurate.

Required:
Identify the validities as either higher or lower priority in the context of this experiment.