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 338 floppy disks is drawn. Of these disks, 318 were not defective. Using the data, construct the 85% confidence interval for the population proportion of disks which are defective. Round your answers to three decimal places.

Answer 1

Sample proportion of defective = = (338 - 318) / 338 = 0.059

85% confidence interval for p is

- Z * sqrt ( ( 1 - ) / n) < p < + Z * sqrt ( ( 1 - ) / n)

0.059 - 1.4395 * sqrt( 0.059 * 0.941 / 338) < p < 0.059 + 1.4395 * sqrt( 0.059 * 0.941 / 338)

0.041 < p < 0.077

85% CI is ( 0.041 , 0.077 )