# Confidence Interval: Nursing school alumi & Auditor for bank

A nursing school wants to estimate the true mean annual income of its alumni. It randomly samples 200 of its alumi. The mean annual income was 55,200 with a standard deviation of 1,500. Find the 95% confidence inteval for the true mean annual income of the nursing school alumni.

2. An auditor wants to estimate what proportion of a bank's commercial loan files are incomplete. The auditor randomly samples 100 files and finds 9 are incomplete. Using a 95% confidence interval, estimate the true proportion of incomplete files for all the bank's commerical loans.

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#### Solution Preview

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Hypothesis testing

A nursing school wants to estimate the true mean annual income of its alumni. It randomly samples 200 of its alumni. The mean annual income was 55,200 with a standard deviation of 1,500. find 95% confidence interval for the true mean annual income of the nursing school alumni.

Answer

Since the sample is fairly large, we can use the normal distribution for the construction of CI.

The confidence interval is given by

Confidence Interval Estimate for the Mean

Data ...

#### Solution Summary

The solution provides step by step method for the calculation of confidence interval for mean. Formula for the calculation and Interpretations of the results are also included. Interactive excel sheet is included. The user can edit the inputs and obtain the complete results for a new set of data.