Estimation in Sampling

Hello,
I would like some assistance in solving the following problem;

Researchers want to estimate the mean farm acreage in Canada. The estimate must be correct to within 25 acres with probability 0.95. A preliminary study suggests that 80 acres is a reasonable guess for the standard deviation. How large a sample of farm is required?

Usually \(\displaystyle \frac{z_{\alpha}^{2}\cdot s^{2}}{d^{2}}\)

What values have you and which must you look up?

The only values given are posted; 25 acres with probability 0.95. the preliminary study suggests that 80 acres is a reasonable guest for the standard deviation.
Given the .95, for the total area of the bell, I believe dividing it by 2 would provide a half (.475) then the Z value for that would be .196, so hopefully these values will help.

Thanks

DAT

What? Please read the informatino provided.

donovantulloch said:

Researchers want to estimate the mean farm acreage in Canada. The estimate must be correct to within 25 acres with probability 0.95. A preliminary study suggests that 80 acres is a reasonable guess for the standard deviation. How large a sample of farm is required?

Click to expand...

d = 25
s = 80

You have to do some of the work. Give z another try.