For question 18 I can work out the critical value for a 98% and a 90% confidence interval, but is there a way to find p? Please note the numbers given should be read as [75.38, 86.52].

Also, for Q19, would option 4 be correct?

Question 18 A 98% confidence interval estimate for a population mean / is determined to be [75 38, 86 52] If the confidence level is reduced to 90% the confidence interval for u 1 Becomes wider 2 Remains the same 3 Becomes narrower 4 Lower limit of 98% confidence interval will be equal to lower limit of the 90% confidence interval 5 None of the above answers is correct Question 19 David Copperfield thinks that the prices of a certain type of "biased" coin are normally distributed with a variance of 4 He conducts a survey of 7 magic stores and finds the coins priced at the following R52, R49, R54, R52. R50, R51 and R48 A 90% confidence interval for the population mean of the price (to 2 decimal places) is 1 (49 61, 52 10) 2 (50 39, 51 33) 3 (47 57, 54 15) 4 (49 38, 52 34) 5 (50 10, 51 61)