Pineapple produces a computer mouse. A scroll wheel is one of the most important components. To check its quality, four samples were taken during four successive days and then the diameter of each unit was measured. The results are in the following table. Table for factors for control limits is also given. The company needs to determine whether the process has been stable during this period. Day 1 Day 2 Day 3 Day 4 Sample 1 3 5 4 3 Sample 2 3 3 3 4 Sample 3 2 3 3 2 Sample 4 4 4 3 1 Number of observations in subgroup Factors for process mean chart (A2) Factors for process variation chart upper control limit (D4) 3 1.023 2.574 4 0.729 2.282 5 0.577 2.114