One of the stages in the process of making denim cloth at the Western Mills Company is to spin cotton yarn onto spindles for subsequent use in the weaving process. Occasionally the yarn breaks during the spinning process, and an operator ties it back together. Some number of breaks is considered normal; however, too many breaks may mean that the yarn is of poor quality. To monitor this process, the quality-control manager randomly selects a spinning machine each hour and checks the number of breaks during a 15-minute period. Following is a summary of the observations for the past 20 hours:

Construct a c-chart using 3σ limits for this process and indicate if the process was out of control at any time.

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Sample Number of Breaks 3 2. 2. 3 4 6. 3 4 10 11 3 12 4 13 6. 14 15 16 6. 17 18 19 8. 20 6.