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    c.  Is it reasonable to conclude that Internet executives have a mean stress level in the dangerous level, according to Dr. Benner’s test?

Problem # 50

Families USA, a monthly magazine that discusses issues related to health and health costs, surveyed 20 of its subscribers. It found that the annual health insurance premiums for a family with coverage through an employer averaged $10,979. The standard deviation of the sample was $1,000.

    a.  Based on this sample information, develop a 90% confidence interval for the population mean yearly premium.

    b.  How large a sample is needed to find the population mean within $250 at 99% confidence?