Two different hardening processes—(1) saltwater quenching and (2) oil quenching—are used on samples of a particular type of metal alloy. The results are shown in Table 4E.2. Assume that hardness is
(a) Test the hypothesis that the
hardness for the oil quenching process. Use
(b) Assuming that the variances
(c) Construct a 95% confidence interval on the ratio
(d) Does the assumption of normality seem appropriate for these data?
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