A sample of 35 workers was randomly selected from a workforce of 110 to estimate the average amount spent weekly at the canteen. The sample mean was £5.40 and the sample standard deviation was £2.24:...

A sample of 35 workers was randomly selected from a workforce of 110 to estimate the average amount spent weekly at the canteen. The sample mean was £5.40 and the sample standard deviation was £2.24:

a. Calculate a 95 per cent confidence interval for the mean.

b. What sample size would be required to estimate the mean to within�}£0.50 with a 95 per cent confidence interval?