Find the confidence interval for single mean
A sample of 20 pages was taken without replacement from the 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 a large block of multicolored illustrations, maps, text). The data (in square millimeters) are shown below:
0

260

356

403

536

0

268

369

428

536

268

396

469

536

162

338

403

536

536

130

a) Construct a 95% confidence interval for the true mean.
b) What may normality be an issue here?
c) What sample size would be needed to obtain an error of +/ 10 square millimeters with 99 percent confidence?
d) If this is not a reasonable requirement, suggest one that is.