Provide a 99% CI for the mean difference in median gray levels between cataractous and normal eyes?

Ophthalmology

A camera has been developed to detect the presence of cataract more accurately. Using this camera, the gray level of each point (or pixel) in the lens of a human eye can be characterized into 256 gradations, where a gray level of 1 represents black and a gray level of 256 represents white. To test the camera, photographs were taken of 6 randomly selected normal eyes and 6 randomly selected cataractous eyes (the two groups consist of different people). The median gray level of each eye was computed over the 10,000+ pixels in the lens. The data are given in Table 8.14.

Table 8.14: Median gray level for cataractous and normal eyes

 

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Normal median gray level Cataractous median gray level Patient number 161 158 2 140 182 3 136 185 4 171 145 106 167 177 149 143.8 169.0 х 22.7 15.4