Statistical Analysis

Levels of groups’ certainties about their eyewitness testimony to a simulated crime were compared. The first group was set up to be “right” in its eyewitness accounts and the second group was set up to be “wrong”; the desire was to see if confidence differed across groups.

Thirty-four participants were recruited from a college campus and randomly divided into two groups, both of which were shown a video of a crime scenario (length: 58 seconds) in which the perpetrator’s facial characteristics (with respect to the camera) were clearly visible at two separate points and sporadically visible at others.

Half the participants then were shown a five-individual lineup that contained the perpetrator in the video (“Group A”), and half the participants were shown a five-individual lineup that did not contain the perpetrator (“Group B”). Participants were asked to (a) identify if and where the perpetrator was in the lineup and (b) provide a rating of confidence on a scale from 1 to 10 (10 being highly confident) that the selection was the same as the person seen in the video committing the crime.

All participants signed consent forms, were told they could leave the study at any time, and were told they would be debriefed. Data on the confidence ratings are shown in attachments.