Confidence interval

Question

The amount of trash generated by US households (in lbs per day) is Normally distributed. You a random sample of 8 people gives you an average of 10.00 lbs and a sample stdev of 5 lbs. What is the margin of error for a 90% Conf. Int. for the mean? (Leave your answer to two decimal places.)

Answer 1

n=8= sample size, xbar=mean= 10 lbs, s= 5= standard deviation

alpha = 10% = .10, for 90% CI, what is MOE = Margin Of Error?

two tails, df = degrees of freedom =n-1 = 7

calculate t critical value from t tables

MOE = t crtical times s/sqr(n) = t value times 5/sqr8 = t times 5sqr8/8

CI = xbar +/- t(5/8)sqr8 = 10+/-t(5/8)sqr8