Question

A quality-conscious disk manufacturer wishes to know the fraction of disks his company makes which are defective.

Step 2 of 2 :  

Suppose a sample of 1067 floppy disks is drawn. Of these disks, 1025 were not defective. Using the data, construct the 80%80% confidence interval for the population proportion of disks which are defective. Round your answers to three decimal places.

Answer 1

n = 1067

P(defective), p = (1067 - 1025) / 1067 = 0.039

Z for 80% confidence interval = Z_0.1 = 1.28

confidence interval

                              

                              

                               = (0.031 , 0.047)