Questions: Question 6 of 8, Step 2 of 2
8 / 12
Correct
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 865 floppy disks is drawn. Of these disks, 69 were defective. Using the data, construct the 95% confidence interval for the population proportion of disks which are defective. Round your answers to three decimal places.
Lower endpoint: Upper endpoint:
Transcript text: Question 6 of 8, Step 2 of 2
$8 / 12$
Correct
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 865 floppy disks is drawn. Of these disks, 69 were defective. Using the data, construct the $95 \%$ confidence interval for the population proportion of disks which are defective. Round your answers to three decimal places.
Answer
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Lower endpoint: $\square$ Upper endpoint: $\square$
Solution
Solution Steps
Step 1: Calculate the sample proportion of defective items
Given a sample size of 865 and 69 defective items, the sample proportion \(p\) is calculated as \(p = \frac{69}{865} = 0.0798\).
Step 2: Calculate \(q = 1 - p\)
\(q = 1 - 0.0798 = 0.92\).
Step 3: Determine the Z-score
For a confidence level of 95%, the Z-score is approximately 1.96.
Step 4: Calculate the standard error of the proportion
The standard error \(SE\) is calculated as \(SE = \sqrt{\frac{p \cdot q}{n}} = 0.0092\).
Step 5: Calculate the margin of error
The margin of error \(ME\) is \(ME = Z \cdot SE = 0.0181\).
Step 6: Determine the confidence interval
The confidence interval is from 0.062 to 0.098.
Final Answer:
The 95% confidence interval for the population proportion of defective items is from 0.062 to 0.098, rounded to 3 decimal places.