IQ tests are designed to yield results that are approximately normally distributed. Researchers think that the population standard deviation is 15. A reporter is interested in estimating the average IQ of employees in a large high-tech firm in California. She gathers the IQ information on 22 employees of this firm and records the sample mean IQ as 106.

a. Compute 90% and 99% confidence intervals of the average IQ in this firm.

b. Use these results to infer if the mean IQ in this firm is significantly different from the national average of 100. P-69