Only b

Problem 3 (8) To have an idea about the expected earnings of his (to be opened) Gentle Lentil Restaurant, John collected data on the monthly earnings in January of a random sample of 25 restaurants of similar size and offering similar menu to his planned restaurant, The sample mean of earnings was $11, 776 and the sample standard deviation was $6, 000. a) Construct a 95% confidence interval for the mean monthly earnings in January and state the assumption required for the validity of the constructed interval.(4) b) John then collected data on the monthly earnings for 144 randomly sampled restaurants in February, which gave the sample mean = $20,000 and sample standard deviation = $5460 from which he obtained the following confidence interval for the mean earnings in February (18, 930.85, 21060.15). What is the confidence level of the interval that John obtained? (4)