Question: A telecommunication company wants to estimate the mean length of time (in minutes) that 18-to-24 year olds spend text messaging each day. In a random sample of twenty-seven 18-to-24 year olds, the mean length of time spent text messaging was 29 minutes. From past studies, the company assumes that the population standard deviation is 4.5 minutes. Assume that text messaging times are normally distributed. You will need to decide whether to use the normal distribution or the t-distribution, and then construct the 90% confidence interval for the population mean m number of minutes 18-to-24 year olds spend text messaging each day.