statistics
posted by Tom .
A statistics practitioner would like to estimate a population mean to within 50 units with 99% confidence given that the population standard deviation is 250.
a) What sample size should be used.
b) Repeat part (a) with a standard deviation of 50.
c) Repeat part (a) using a 95% confidence level.
d) Repeat part (a) when we wish to estimate the population mean to within 10 units.

Formula:
n = [(zvalue * sd)/E]^2
...where n = sample size, use a ztable to represent the 99% confidence interval, sd = 250, E = 50, ^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 50 for sd.
For c), use 95% interval.
For d), use 10 for E.
I hope this will help get you started. 
mn

a)166
b)7
c)97
d)4148
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