# statistics

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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 -

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 -

10

• statistics -

106

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