Fifteen samples of size 100 were taken from a production of containers. The numbers of defectives (leaking containers) in those samples (in the order observed) were

1 4 5 4 9 7 0 5 6 13 0 2 1 12 8

From previous experience it was known that the average fraction defective is p = 4% provided that the process of production is running properly. Using the binomial distribution, set up a fraction defective chart (also called a p-chart), that is, choose the LCL = 0 and determine the UCL for the fraction defective (in percent) by the use of 3-sigma limits, where σ² is the variance of the random variable

X̅ = Fraction defective in a sample of size 100. Is the process under control?