From a sample of 61 A-level mathematics students, the sample mean mark in the final examination was 62. The sample variance in the final examination was 25. 4 a) Find the 95% confidence interval for the population mean mark for the final examination. + b) What factor(s) would result in a decrease/increase in the size of the 95% confidence interval? If the sample size was just 10, would the method and answer in part a) be valid?