Refer to Exercise 11. An assignable cause was found for the unusually high sample average refractive index

Question:

Refer to Exercise 11. An assignable cause was found for the unusually high sample average refractive index on day 22. Recompute control limits after deleting the data from this day. What do you conclude?
Exercise 11
The accompanying table gives sample means and standard deviations, each based on n = 6 observations of the refractive index of fiber-optic cable. Construct a control chart, and comment on its appearance. ˆ‘xÌ…i = 2317.07 and ˆ‘si = 30.34.