Scott Paper tests its toilet paper by subjecting 15 rolls to

Scott Paper tests its toilet paper by subjecting 15 rolls to a wet stress test to see whether and how often the paper tears during the test. Following are the number of defectives found over the last 15 days: 2, 2, 1, 1, 1, 3, 4, 4, 1, 1, 2, 2, 2, 2 and 2.

Solution

Mean of 15 observations = 2

Standard deviation = 1

Control limits = (Mean - 3*Standard deviation, Mean + 3*Standard deviation)

= (2 - 3, 2 + 3)

=(0, 5) [As, number of times a paper tears can\'t be negative]