Effective Lineup Size
A lineup's effective size is the number of plausible or "effective" lineup members. For example, an effective size of 4 implies the lineup has four plausible lineup members. It is calculated from the distribution of choices in the lineup. This calculator uses the formula from Tredoux (1998). To calculate effective size, enter the identification frequency for each lineup member.
Tredoux, C. G. (1998). Statistical inference on measures of lineup fairness. Law and Human Behavior, 22(2), 217-237.