Posted by **----** on Thursday, November 21, 2013 at 11:11am.

The standard deviation for a population is σ = 15.3. A sample of 36 observations selected from this population gave a mean equal to 74.8.

a) Make a 90% confidence interval for μ

b) Construct a 95% confidence interval for μ.

c) Determine a 99% confidence interval for μ.

d) Does the width of the confidence intervals constructed in parts a through c increase as the confidence level increases? Explain your answer

- Statistics -
**PsyDAG**, Thursday, November 21, 2013 at 11:24am
% = mean ± ? SEm

SEm = SD/√n

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability ([1-%]/2) to find the Z score. Insert that into ? position.

Example: 95% = 74.8 ± 1.96 SEm

After you do a through c, you should be able to explain.

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