Americans shop for groceries week after week.

Can you please assist, preferably without using excel for explanations!

Americans shop for groceries week after week. A website builder from Texas has developed a new approach to increase sales by decreasing the time people spend visiting the grocery stores by creating an online grocery website. To minimize the risk of loosing customers online, the owner of the business requests a test of the new marketing strategy, for a small unimportant segment of her market. In one week test, 36 people spent an average of 15 minutes visiting her site with a standard deviation of 5 minutes.

(a) What is the 99% confidence interval for the average amount of time all web customers of her company will spend visiting the new website?

(b) Interpret the confidence interval obtained in part (a) to a layperson.

(c) Do we need to assume the distribution of the time all customers spend visiting the new web site is normally distributed for the interval found in (a) to be valid? explain.

(d) The company's success criterion is based on getting customers to spend on average at least 20 minutes on the web site. Using your answer in (a) , is there sufficient reason to believe that the new strategy has been successful?

(e) Suppose we want a 95% confidence interval for the population mean with (+ or - 1 minute). What sample size is needed? (assume the standard deviation remains 5 minutes)