For the first six months of the year, an analyst records the monthly closing stock price (in $) for a firm as: 90, 95, 96, 99, 91, 93. (You may find it useful to reference the t table.) ExpictureClick 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 94.00 Sample standard deviation 3.34b. Calculate the 95% 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