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Athletes performing in bright sunlight often smear black eye grease under their

ID: 3156797 • Letter: A

Question

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 sensitivity to contrast after three hours facing into bright sun, both with and without eye grease. (Greater sensitivity to contrast improves vision and glare reduces sensitivity to contrast.) This is a matched pairs design. here are the differences in sensitivity, with eye grease minus without eye grease. contrast.) This is a matched pairs design. Here are the differences in sensitivity, with eye grease minus without eye grease. How much more sensitive to contrast are athletes with eye grease than without eye grease? Give a 99 % confidence interval to answer this question. (Round your answer to three decimal places.) You may need to use the appropriate appendix table to answe this question.

Explanation / Answer

From information given, dbar=0.1019, sd=0.2296, N=16 pairs

The 99% c.i=xbar+-t15,0.01SE(dbar), where SE(dbar)=sd/sqrt n

=0.1019+-2.947*(0.2296/sqrt 16)

=-0.067 to 0.271