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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,
% = 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. 
Statistics 
JP,
In a recent study, 25 males used a new weightloss supplement, and all but 6 of them experienced weight loss after two weeks. In the same study, 100 females used the same supplement, and all but 31 of them experienced weight loss after two weeks.
Fill in the blanks of the statement below to make the statement the most reasonable possible.