For the following confidence interval problems, give the estimate, the margin of
ID: 3230612 • Letter: F
Question
For the following confidence interval problems, give the estimate, the margin of error, and the lower and upper bounds. Write a sentence of conclusion. Show work whenever asked. Round your estimate and margin of error to 4 significant digits. a) A mail-order company promises its customers that the products ordered will be mailed within 72 hours after an order is placed. The quality-control department at the company checks from time to time to see if this promise is fulfilled. Recently the quality-control department took a sample of 50 orders and found that 35 of them were mailed within 72 hours of the placement of the orders. Construct a 90% confidence interval for the percentage of all products ordered that are mailed within 72 hours of the placed order. Use the plus-four method. Calculate by hand: do not use TESTS on your calculator.Explanation / Answer
here point estimate p=35/50=0.7
std error of proportion =(p(1-p)/n)1/2 =0.0648
for 90% CI; z=1.645
hence confidence interval =point estimate -/+ z*std error =0.5934 ; 0.8066