Posted by **Anonymous** on Saturday, February 4, 2012 at 10:43pm.

A researcher is interested in

estimating the average salary of teachers in a large urban

school district. She wants to be 95% confident that her

estimate is correct. If the standard deviation is $1050, how

large a sample is needed to be accurate within $200?

- statistics -
**MathGuru**, Saturday, February 4, 2012 at 10:49pm
Formula:

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

...where n = sample size, z-value will be 1.96 using a z-table to represent the 95% confidence interval, sd = 1050, E = 200, ^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.

- statistics -
**Anonymous**, Thursday, December 18, 2014 at 9:24am
10

- statistics -
**Anonymous**, Thursday, December 18, 2014 at 9:27am
106

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