a. Calculate the sample mean and the sample standard deviation. (Round final answer to 2 decimal places.) Sample mean Sample standard deviation b. Calculate the 99% confidence interval for the mean stock price of the firm assuming that the stock price is normally distributed. (Round final answer to 2 decimal places.) Confidence interval to c. What happens to the margin of error if a higher confidence level is used for the interval estimate? O The margin of error increases as the confidence level increases. O The margin of error decreases as the confidence level increases.Exercise 8-39 Algo A random sample of 35 observations results in 14 successes. (You may find it useful to reference the z table.) a. Construct the 95% confidence interval for the population proportion of successes. (Round final answers to 3 decimal places.) Confidence interval to b. Construct the 95% confidence interval for the population proportion of failures. (Round final answers to 3 decimal places.) Confidence interval toExercise 8-31 Algo For the first six months of the year, an analyst records the monthly closing stock price (in $) for a firm as: 160, 168, 162, 169, 167, 165. (You may find it useful to reference the t table.) ? Click here for the Excel Data File a. Calculate the sample mean and the sample standard deviation. (Round final answer to 2 decimal places.) Sample mean Sample standard deviation b. Calculate the 99% confidence interval for the mean stock price of the firm assuming that the stock price is normally distributed. (Round final answer to 2 decimal places.) Confidence interval to