Thirty samples were selected to estimate the percentage of titanium in an aerospace alloy. The standard deviation of the sample was calculated as s = 0.37. The population is assumed to be normally...

Thirty samples were selected to estimate the percentage of titanium in an aerospace alloy. The standard deviation of the sample was calculated as s = 0.37. The population is assumed to be normally distributed. According to this,
a) Calculate the 95% confidence interval for the standard deviation.
b) Can it be said at the 5% significance level that the standard deviation of the population is ?(sigma) = 0.25 ?