23. Twelve rolls of wallpaper have been examined to estimate the average number of de- fects per roll. The number of defects found in each was 2, 2, 3, 5, 1, 6, 4, 5, 7, 0, 3, and 1, respectively. The wallpaper manufacturer paid careful attention to the process to make sure it was in control when these samples were taken. Establish limits that can be used to determine whether the process remains in control when the sampling unit is one roll of wallpaper.