A sample of 100 observations is selected from an unknown population for which the population standard deviation is 9. The sample mean is 100. (a) Find a 95% confidence interval for population mean. | (b) Do you think that the width of 99% confidence interval will be wider than 95% confidence interval? Justify your answer. (c) If we get another sample of 200 observations from this population, find the 95% confidence interval for population mean. What can you say about the effect on the confidence interval when the sample size is increased from 100 to 200?