6. (5 points) This question is similar to Exercise 14 on page 363 of the textbook. The population is normally distributed. A sample produced the following observations. 13 9 8 7 7 11 8 2 a. Calculate the sample mean and the sample standard deviation. Show your work with the table as page 114 of the course packet. You may use Excel to construct the table with arithmetical formulas and function "=sum." Don't use other Excel functions. b. Enter the data in Excel and use Data Analysis to get the descriptive statistics printout. c. What is the margin of error for a 95% confidence interval for the population mean? d. Construct the 95% confidence interval for the population mean. e. Construct a 78% confidence interval for the population mean. Hint: Use Excel function =t.inv.2t to find the value of t for the interval calculation