Please help I am so lost and my book shows me nothing helpful. You are interested in the incomes of your customers. A sample of 100 customer incomes yields a standard deviation of $141,421 and a mean of $300,000:

Question

Please help I am so lost and my book shows me nothing helpful. You are interested in the incomes of your customers.  A sample of 100 customer incomes yields a standard deviation of $141,421 and a mean of $300,000:

a.	Determine the point estimate

b.	Determine the interval estimate at the 95% confidence level

c.	Determine what percent of the population would have a salary above $455,000

PsyDAG · Answer

a. Best point estimate from your data is your sample mean.

b. 95% = mean ± 1.96 SEm

SEm = SD/√n

c. Z = (score-mean)/SD

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.