1. A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period of time.
   At least 500 hours:
2. Find the area under the normal curve for the condition.
   Find the percent of the area between the mean and 3.01 deviations from the mean.
3. The following chart shows the percent of the U.S. population that was age 65 and over the years 1970, 1980, 1990, 1995, and 2000, where the column labeled Year refers to the number of years since 1970.

Percent of U.S Population Age 65 and Over

Year        Percent

0              9.8

10            11.3

20            12.5

25            12.8

30            12.4

1. Construct a Scatter diagram placing the year on the horizontal axis.
2. Use the scatter diagram in part (a) to determine whether you believe that a correlation exists between the year and the percent of the U.S. population age 65 and over. Explain.
3. Determine the correlation coefficient between the year and the percent of the U.S. population age 65 and over.
4. Determine whether a correlation exists at a(alpha) = .05.
5. Assuming that this trend continues, determine the equation of the line that best fit between the year and the percent of the U.S. population age 65 and over.
6. Use the equation in part (e) to predict the percent of the U.S. population age 65 and over in 2010, or 40 years after 1970.

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Solution: The downloadable solution consists of 4 pages, 389 words and 3 charts.
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