1 In a study comparing individual performance with group performance, Laughlin, Zander and Knievel, and Tan (2003) found that groups consistently outperformed the best of individuals. The task was a letters-to-numbers problem in which an arithmetic problem was presented substituting a letter in place of each digit. Participants had to determine which letters corresponded to each number. Scores were compared between 3-person groups and the best of individuals. The number of trials it took for the participants to solve each problem was measured, where the fewer number of trials required to solve a problem indicated better performance. The following data is similar to those obtained in their study.

Groups	Individuals
n=15	n=15
M= 3.8	.7
.4	.2

• Based on the results, is there a significant difference between performance for individuals versus the performance for groups? Use a two-tailed test with =.05.
• If there is a significant difference compute the estimated value of Cohens d and r².