A random sample of 60 students was taken in two different universities. The first sample had an average mark of 77 and a standard deviation of 6. The second sample had an average mark of 68 and a standard deviation of 10.
(a) Find a 95 % confidence interval for the difference between the mean marks in the two universities.
(b) What increase in the sample size would be necessary to cut the error allowance by 1/2?
(c) What increase in the sample size would be necessary to reduce the error allowance to 1.0?