Posted by **Shannon** on Thursday, October 6, 2011 at 12:08am.

A researcher wishes to be 95% confident that her estimate of the true proportion of individuals who travel overseas is within 4% if the true proportion. Find the sample necessary if in a prior study, a sample of 200 people showed that 40 traveled overseas last year. If no estimate of the same proportion is available, how large should a sample be????

show your work please so i can understand :P

- Stat Help -
**MathGuru**, Thursday, October 6, 2011 at 12:01pm
Try this formula:

n = [(z-value)^2 * p * q]/E^2

Note: n = sample size needed; use 40/200 for p (convert to a decimal); use 1 - p for the value of q. E = maximum error, which is .04 for 4%. Z-value is found using a z-table (for 95% confidence). Note: ^2 means squared and * means to multiply.

I'll let you take it from here.

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