2 ) Assuming normal distribution, a 95% confidence interval for the population mean when n=25 a sample standard deviation gives a sample standard deviations=3 and a sample mean = 58.3 is: a. (57.06, 59.54) b. (57.12, 59.48) c. (-57.12, 59.54) d. (-2.93, 2.93) 3)A point estimate for the population standard deviation based on an unbiased estimator of the population variance when a sample 2, 3, 4, 7 and 10 is drawn from a normal population with unknown mean and unknown variance is: a. 4 b. 42.8 c. 3.27 approximately d. 10.7 4)Find the sample size n, that is necessary if the width of the the 95% confidence interval is to be 0.4. Take = 1.5 a. 217 b. 200 c. 15 d. 14