Question

3. A recent study collected a simple random sample of n = 400 college women and found that 82% of them were employed during Summer. Compute the 90% confidence interval for p based on ˆp

Answer 1

The confidence interval for population proportion is calculated as

Where,

Z=1.645 calculated by Z table shown below

n=400 and ^p=0.82 hence by formula

Margin of error=E

So, confidence interval=0.82+/-0.032

{0.788, 0.852} or 0.788<p<0.852

Table for Z score as