Explore BrainMass

Confidence Intervals with Household Income

If 400 households have an annual average income of $50,000 with a standard deviation of $4,000, what is the 90% confidence interval that includes the population household income?

Please show all steps of the work, so tht I can understand the formulas/process.

Solution Preview

Given sample mean xbar=50000, sample standard deviation s=4000, sample size n=400. For a 90% confidence level, z=1.645. So, by a formula ...

Solution Summary

Solution shows how to find the population income at a 90% confidence interval.