Question 923323
 mean = 12 hours, with a standard deviation = 3.5 hours.
estimate the mean viewing time within one-quarter hour. 
The 90 percent level of confidence is to be used.
ME = .25 = 1.645(3.5/sqrt(n)
n = {{{(1.645*3.5/.25)^2}}} = 531 rounded Up to whole number