You have been running a repeated measures experimental design during spring quarter. The experiment examined people's facial recognition ability under three different kinds of stress. The stress conditions were created during the experiment and can be divided into Low (level 1), Medium (level 2), and High (level 3). The same group of 10 people went through all three stress treatments, but on different days over three weeks (i.e. a participant did level 1, and then returned a week later and did level 2, and so on). Each time you measured the participant's ability to recognize different emotional facial expressions. (Assume the test is valid for the measure.) You discover that half of your subjects had a very difficult and stressful midterm immediately before the final session of testing. What concern would this specifically raise for your design? There may be carryover effects due to practice. There may be a problem due to history effects. There may be a problem due to maturation effects. None of the above issues are a concern for a repeated measures design.
