Question

2. You work in quality control for a manufacturer, and want to see what proportion of your company’s products pass inspection. You take a sample of 80 products, and find that 65 of them pass inspection.

a. What is your point estimate for the proportion that pass

b. Use your answer from a) to find a 95% CI for ‘p’ (Remember, you are allowed to

use the ‘short-cut’ formula here)

c. You want your CI to be accurate to ±1.5 percentage points. How large should

your sample size be if

i. You use your estimate of p from part a)

ii. You make no assumptions as to the value of p

Answer 1

2(a)

The point estimate for the proportion that pass inspection is

(b)

(c)

(ii)

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