Posted by **Tom** on Saturday, March 13, 2010 at 9:26pm.

Calculate the following:

a) Determine the sample size necessary to estimate a population mean to within 1 with a 90% confidence given that the population standard deviation is 10.

b) Suppose that the sample was calculated at 150. Estimate the population mean with 90% confidence.

- Statistics -
**MathGuru**, Monday, March 15, 2010 at 6:51pm
Formula for a):

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

...where n = sample size, z-value will be found using a z-table to represent the 90% confidence interval, sd = 10, E = 1, ^2 means squared, and * means to multiply.

Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.

For b) Use a confidence interval formula:

CI90 = mean + or - z-value (sd/√n)

I'll let you take it from here.

- Statistics -
**Anonymous**, Wednesday, December 5, 2012 at 1:29am
10

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