# detecting HIV.

6. STDAlert provides a blood test for detecting HIV. Sometimes the test provided gives false positive results. The medical director claims that the rate of false positives is 2%. To aIDress this issue, they conducted a study of 300 blood donors randomly selected who do not have HIV and found that 3 received a false positive result. At Î±=0.05 is there enough evidence to reject the claim? Test the claim about the population proportion.

7. A recent article in Business Week listed the Best Small Companies. We are interested in the current results of the companies’ sales and earnings. A random sample of 12 companies was selected and the sales and earnings, in millions of dollars, are reported below.

 COMPANY Sales (\$millions) Earnings (\$millions) COMPANY Sales (\$millions) Earnings (\$millions) Papa John International \$89.2 \$4.9 Checkmate Electronics \$17.5 \$2.6 Applied Innovation 18.6 4.4 Royal Grip 11.9 1.7 Integracare 18.2 1.3 M-Wave 19.6 3.5 Wall Data 71.7 8.0 Serving-N-Slide 51.2 8.2 Davidson Associates 58.6 6.6 Daig 28.6 6.0 Chico’s Fas 46.8 4.1 Cobra Golf 69.2 12.8

Let sales be the independent variable and earnings be the dependent variable.

1. Draw a scatter plot.
2. Compute the coefficient of correlation
3. Compute the coefficient of determination.
4. Interpret the findings in (b) and (c).
5. Determine the regression equation.
6. For a small company with \$50.0 million in sales, estimate the earnings.

8. United Way sought to analyze its donors to determine if there was a linear relationship family income level and percent of income donated to the United Way. The income levels (in thousands) and the corresponding percent of family income donated is presented in the table below. The table reflects information for seven families. Use Î±= 0.05 to a) display data in a scattered plot, b) calculate the correlation coefficient, and c) test the significance of the correlation coefficient.

 Income Level, x 50 65 48 42 59 72 60 Donating Percent, y 4 8 5 5 10 7 6

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