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 given below:-

Saltwater Quench

145

152

150

150

153

147

148

Oil Quench

155

141

140

152

146

146

158

154

152

139

151

148

143

For the above data set calculate the following confidence intervals:

(i)95% confidence interval for the population mean of the saltwater quench.

(ii)95% confidence interval for the population standard deviation for the saltwater quench.

(iii)95% confidence interval for the population ratio of variances

(iv)95% confidence interval for the difference in population means

For each confidence interval, interpret the result in the context of the original problem for which the data set was collected.

(40 Marks)