1) -0.004
2) 0.007
3) 0.001
4) -0.003
5) -0.002
6) -0.003
7) -0.005
8) -0.006
9) -0.007
10) -0.002
11) -0.003
12) 0.001
13) 0.005
14) -0.003
15) -0.001
16) -0.006
17) -0.003
18) -0.001
19) -0.013
20) -0.009
One operation of a steel mill is to cut pieces of steel into parts that are used in the frame for front seats in an automobile. The steel is cut with a diamond saw and requires the resulting parts must be cut to be within +/- 0.005 inch of the length specified by the purchaser. The measurement reported from a sample of 20 steel parts (and shown in the table above) is the difference, in inches, between the actual length of the steel part, and the specified length of the steel part.
a. Construct a 99% confidence interval estimate of the population mean difference between the actual length of the steel part and the specified length of the steel part? Round to six decimal places