Research has shown that people are more likely to show dishonest and self-interested behaviors in darkness than in a well-lit environment (Zhong, Bohns, & Gino, 2010). In one experiment, participants were given a set of 20 puzzles and were paid $0.50 for each one solved in a 5-minute period. However, the participants reported their own performance and there was no obvious method for checking their honesty. Thus, the task provided a clear opportunity to cheat and receive undeserved money. One group of participants was testing in a room with dimmed lighting and a second group was tested in a well-lit room. The reported number of solved puzzles was recorded for each individual. The following data represent results similar to those obtained in the study. Well-Lit Room Dimly-Lit Room 7 9 8 11 10 13 6 10 8 11 5 9 7 15 12 14 5 10 a) Is there a significant difference in reported performance between the two conditions? Use a two-tailed test with  = .01. (If you are unsure how to do this, you can instead conduct a two-tailed test with  = .05.) b) Compute Cohen’s d to estimate the size of the treatment effect

Research has shown that people are more likely to show dishonest and self-interested
behaviors in darkness than in a well-lit environment (Zhong, Bohns, & Gino, 2010). In one
experiment, participants were given a set of 20 puzzles and were paid $0.50 for each one
solved in a 5-minute period. However, the participants reported their own performance and
there was no obvious method for checking their honesty. Thus, the task provided a clear
opportunity to cheat and receive undeserved money. One group of participants was testing in a
room with dimmed lighting and a second group was tested in a well-lit room. The reported
number of solved puzzles was recorded for each individual. The following data represent results
similar to those obtained in the study.
Well-Lit Room Dimly-Lit Room
7 9
8 11
10 13
6 10
8 11
5 9
7 15
12 14
5 10
a) Is there a significant difference in reported performance between the two
conditions? Use a two-tailed test with  = .01. (If you are unsure how to do this, you
can instead conduct a two-tailed test with  = .05.)
b) Compute Cohen’s d to estimate the size of the treatment effect