10.74 [EX10-074] When evaluating different measuring instruments, one must first determine whether there is a systematic difference between the instruments. Lenses from two different groups

(1 and 2) were measured once each by two different instruments. The measurement differences

(Instrument A  Instrument B) were recorded.

Measurement units have been coded for proprietary reasons.

Group 1 4 5 2 3 7 10 11 1 3 7 5 3 4

5 7 4 1 18 0 17 12 9 4 17 2 Group 2 13 12 5 11 15 7 33 10 6 2 16 2 0 19 6 17 4 19 22 4 8 10 6 Does there appear to be a systematic difference between the two instruments?

a. Describe each set of data separately using a histogram and comparatively using one side-byside graph.

b. Find the mean and the standard deviation for each set of data.

c. Are the assumptions satisfied? Explain.

d. Test the hypothesis that there is no difference between the means of the two differences. Use   0.05.

e. Is there any evidence of a difference between the two instruments? Explain.