Dr. Hogan carefully chose the final exams written by her best students to read first. They all received excellent grades. After these, she read the rest of the exams and graded most of them average or worse. This is an example of perceptual error.

Contrast effects

Explanation:

In psychology, the contrast effect bias refers to a cognitive bias that affects our perception when we compare similar things, specially when we contrast them with something better or worse. By doing this, we are more aware of the differences between the elements of the group and this can lead to the error or judge them or grade them based on the best or worst elements.

In this example, Dr. Hogan reads first the exams written by her best students. Then she reads the rest and grades them average or worse. We can see that he is comparing similar things (the exams) but it's comparing them based on the best elements of the group (the ones by the best students) and therefore all the rest of them seem poorer and they receive worse grades. Therefore, this is an example of contrast effect perceptual error.

a is the final ! : )