Athletes performing in bright sunlight often smear black eye grease
under their eyes to reduce glare. Does eye grease work? In one study, 16
student subjects took a test of visual sensitivity to light-and-dark contrast.
after three hours facing into bright sun, both with and without eye
grease. This is a matched pairs design. If eye grease is effective, subjects
will be more sensitive to contrast when they use eye grease. The
differences in sensitivity, with eye grease minus without eye grease, are
provided in the table.
Differences in Sensitivity
0.07
0.05
0.64 -0.12
0.02 0.43
-0.05
0.24
0.03
0.14 -0.16
-0.18
-0.11 0.28 0.05 0.29
To access the data, click the link for your preferred software format.
CSV Excel (xls) Excel (xlsx) JMP Mac-Text Minitab14-18 Minitab18+ PC-Text R SPSS TI CrunchIt!
STATE: We want to know whether eye grease increases sensitivity on the average.
Data simulated from a Normal distribution based on information in Brian M. DeBroff and Patricia J. Pahk, "The ability of periorbitally applied antiglare products to
improve contrast sensitivity in conditions of sunlight exposure," Archives of Ophthamology, 121 (2003), pp.
997-1001.
Suppose that the subjects are an SRS of all young people with normal vision, that contrast differences follow a Normal
Histribution in this population, and that the standard deviation of differences is σ = 0.22. Carry out a test of significance.
SOLVE: What is the value of the test statistic? Give your answer to two decimal places.