Probability and statistics

Exercise 11.2 The price (in dollars) of a statistics textbook bought online can vary depending on the online store. A random sample of 24 online stores had mean price x = 209.75 and standard deviation s = 23.14. You may assume that the online prices have an approximately normal distribution. Find a 90% confidence interval for the population mean u of the online price of the statistics textbook. Give your answer rounded to 2 decimal places. Exercise 11.3 A random sample of 13 tablets had a mean battery life of x = 8 hours and a standard deviation of s = 2.5 hours. Assume that the battery life of tablets has a normal distribution. Find a 99% confidence interval for the population mean battery life of all tablets. Exercise 11.4 A random sample of 40 families has mean annual income x = 45 (in thousands of dollars) with standard deviation s = 9.3. You may assume that family annual incomes have an approximately normal distribution. Find a 95% confidence interval for the population mean family annual income /. Exercise 11.5 A random sample of 20 stores has mean annual sales x = 203 (in thousands of dollars) and standard deviation s = 25.3. You may assume that annual sales of all stores are approximately normally distributed. Find a 90% confidence interval for the population mean annual sales u of all stores