A quality-conscious disk manufacturer wishes to know the fraction of disks his company makes which are defective. a. Suppose a sample of 865 floppy disks is drawn. Of these disks, 112 were defective. Using the data, estimate the proportion of disks which are defective.
b. Suppose a sample of 865 floppy disks is drawn. Of these disks, 112 were defective. Using the data, construct the 95% confidence interval for the population proportion of disks which are defective.

a) 0.1295

b) The 95% confidence interval for the population proportion of disks which are defective is (0.1071, 0.1519).

Step-by-step explanation:

Question a:

112 out of 865, so:

Question b:

In a sample with a number n of people surveyed with a probability of a success of , and a confidence level of , we have the following confidence interval of proportions.

In which

z is the z-score that has a p-value of .

For this problem, we have that:

95% confidence level

So , z is the value of Z that has a p-value of , so .  

The lower limit of this interval is:

The upper limit of this interval is:

The 95% confidence interval for the population proportion of disks which are defective is (0.1071, 0.1519).

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step-by-step explanation: