Suppose that you need to estimate the mean number of typographical errors per page in the rough draft of a 400-page book. A careful examination of 10 pages gives an average of 6 errors per page with a standard deviation of 2 errors. Assuming that the data may be looked upon as a random sample from a normal population, construct a 99% confidence interval for the actual average number of errors per page in this book and interpret. In this problem, is the normal model appropriate?