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. [Hint:
xi
2317.07 and
si

30.34.]

Day x s Day x s

1 95.47 1.30 9 96.63 1.48 2 97.38 .88 10 96.50 .80 3 96.85 1.43 11 97.22 1.42 4 96.64 1.59 12 96.55 1.65 5 96.87 1.52 13 97.02 1.28 6 96.52 1.27 14 95.55 1.14 7 96.08 1.16 15 96.29 1.37 8 96.48 .79 16 96.80 1.40

(continued)

Day x s Day x s

17 96.01 1.58 21 97.06 1.34 18 95.39 .98 22 98.34 1.60 19 96.58 1.21 23 96.42 1.22 20 96.43 .75 24 95.99 1.18