Dr. stein is conducting a study on individuals who witnessed or lost loved ones in the 2007 mass shooting at virginia tech. dr. stein finds that individuals who were directly affected by the shooting are far more likely than their peers to report intense fear, anxiety, and depression. this example illustrates

Cohort effect

Explanation:

When there is a variation in a characteristic of an area of study over a span of time which have other factors or characteristics same it is called cohort effects.

Here, the people who witnessed the shooting directly have been shown to have intense fear, anxiety, and depression which is known as the cohort effect. They all have the experience of witnessing the shooting in common.