MathStatistics
posted by Richard on .
Find a confidence interval for ƒÊ assuming that each sample is from a normal population.
a. P x = 14, ƒÐ = 4, n = 5, 90 percent confidence
b. P x = 37, ƒÐ = 5, n = 15, 99 percent confidence
c. P x = 121, ƒÐ = 15, n = 25, 95 percent confidence
Need to show my work/formula
Thanks,

Assuming twotailed test, x = mean, ƒD = Standard deviation:
90% = mean ± 1.645 SEm
SEm = SD/√n = Standard Error of the mean
99% = mean ± 2.575 SEm
95% = mean ± 1.96 SEm
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportions and their related Z scores.