A sample of 20 pages was taken with no replacement from 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured(a display ad is large block of multicolored illustrations, maps, and text). The data (insquare millimeters) are given below:
0 260 356 403 536 0 268 369 428 536 268 396 469 536 162 338 403 536 536 130
a) Make a 95 percent confidence interval for true mean.
b) Why might normality be issue here?
c) What sample size would be required to obtain an error of ±10 square millimeters with 99 percent confidence?
d) If this isn't a reasonable requirement, suggest one that is.