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Chapter 4: Q. 4.4 (page 161)
Answer true or false to each statement, and explain your answers.
a. The graph of a linear equation slopes upward unless the slope is 0 .
b. The value of the y-intercept has no effect on the direction that the graph of a linear equation slopes.
a. False
b. True
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Shortleaf Pines. The data from Exercise 4.80 for volume, in cubic feet, and diameter at breast height, in inches, for shortleaf pines are on the WeissStats site.
Tax Efficiency. In Exercise 4.58, you determined a regression equation that relates the variables percentage of investments in energy securities and tax efficiency for mutual fund portfolios.
a. Should that regression equation be used to predict the tax efficiency of a mutual fund portfolio with of its investments in energy securities? with of its investments in energy securities? Explain your answers.
b. For which percentages of investments in energy securities is use of the regression equation to predict tax efficiency reasonable?
(a) Plot the data points and the first linear equation on one graph and the data points and the second linear equation on another.
(b) Construct tables for
(c) Determine which line fits the data points better according to the least-square criterion.
4.76 PCBs and Pelicans, Polychlorinated biphenyls (PCBs), industrial pollutants, are known to be carcinogens and a great danger to natural ecosystems. As a result of several studies, PCB production was banned in the United States in and by the Stockholm Convention on Persistent Organic Pollutants in . One study, published in by R. Risebrough, is titled "Effects of Environmental Pollutants Upon Animals Other Than Man" (Proceedings of the 6th Berkeley Symposium on Mathematics and Statistics, Vl, University of California Press, Pp. ). In that study, Anacapa pelican eggs were collected and measured for their shell thickness, in millimeters (mm), and concentration of PCBs, in parts per million (ppm). The data are on the Weiss Stats site.
a. Obtain a scatterplot for the data.
b. Decide whether finding a regression line for the data is reasonable. If so, then also do parts (c)-(f).
In Exercise 4.5, we give linear equations. For each equation,
a. find the -intercept and slope.
b. determine whether the line slopes upward, slopes downward, or is horizontal, without graphing the equation.
c. use two points to graph the equation.
Given equation is,
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