# Calculating mean, critical t-value, sample size

1. A local bank needed information concerning the checking account balances of its customers. A random sample of 15 accounts was checked. The mean balance was $686.75 with a standard deviation of $256.20. Find a 98% confidence interval for the true mean. Assume that the account balances are normally distributed.

2. Find the critical t-value that corresponds to c=0.90 and n=15.

3. A survey of 100 fatal accidents showed that 35 were alcohol related. Find a point estimate for p, the population proportion of accidents that were alcohol related.

4. The grade point averages of 10 randomly selected students are listed below. Construct a 90% confidence interval for the population standard deviation. Assume the data are normally distributed.

2.0 3.2 1.8 2.9 0.9 4.0 3.3 2.9 3.6 0.8

5. A university dean is interested in determining the proportion of students who receive some sort of financial aid. Rather than examine the records for all students, the dean randomly selects 200 students and finds that 118 of them are receiving financial aid. If the dean wanted to estimate the proportion of all students receiving financial aid to within 2% with 95% reliability, how many students would need to be sampled?

#### Solution Summary

This solution calculates several statistics values including mean, critical t-value and sample size