Answer Happy

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 the following table. Assume
that hardness is normally distributed.
(1) Assuming that the variances 𝜎1 2 and 𝜎2 2 are equal,
construct a 95% confidence interval on the difference in mean
hardness.
(2) Construct a 90% confidence interval on the ratio 𝜎1 2 𝜎2 ⁄
2. Does the assumption made earlier of equal variances seem
reasonable?
Saltwater Oil Quench Quench 145 152 150 150 153 147 148 155 141 140 152 146 146 158 154 152 139 151 148 143