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 195 floppy disks is drawn. Of these disks, 11 were defective. Using the data, construct the 80% confidence interval for the population proportion of disks which are defective. Round your answers to three decimal places.

Answer 1

Sample proportion = 11 / 195 = 0.056

80% confidence interval for p is

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

0.056 - 1.2816 * sqrt( 0.056 * 0.944 / 195) < p < 0.056 + 1.2816 * sqrt( 0.056 * 0.944 / 195)

0.035 < p < 0.077

80% CI is (0.035 , 0.077)