The following data shows the strength(in Pascal) of material A and B A: 198 199 199 200 202 203 204 206 B: 197 198 200 200 200 202 204 The strength of these materials follow normal distribution. i) Construct a 95% confidence interval for the standard deviation of the strength for material A. ii) Test the mean strength of material A is more than 200 Pascal at significance level α = 0.05.
iii) Construct a 95% confidence interval for the difference of mean strength of material A and B if the variances are the same. iv) Based on the results in Question (iii) test the mean strength of material A and B are the same at significance level α = 0.05.