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Chapter 3: Q. 36 (page 191)
An eccentric professor believes that a child with an IQ should have a reading test score and that the reading score should increase by a point for every additional point of IQ. What is the equation of the professor鈥檚 regression line for predicting reading scores from IQ?
The equation is.
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Marijuana and traffic accidents (1.1) Researchers in New Zealand interviewed drivers at age
They had data on traffic accidents and they asked the drivers about marijuana use. Here are data on the numbers of accidents caused by these drivers at age , broken down by marijuana use at the same age
(a) Make a graph that displays the accident rate for each class. Is there evidence of an association
between marijuana use and traffic accidents?
(b) Explain why we can鈥檛 conclude that marijuana use causes accidents.
57. Bird colonies Refer to Exercises and . For the regression you performed earlier, and . Explain what each of these values means in this setting.
Oil and residuals The Trans-Alaska Oil Pipeline is a tube that is formed from -inch-thick steel and carries oil across miles of sensitive arctic and subarctic terrain. The pipe segments and the welds that join them were carefully examined before installation. How accurate are field measurements of the depth of small defects? The figure below compares the results of measurements on defects made in the field with measurements of the same defects made in the laboratory. The line is drawn on the scatterplot.
(a) Describe the overall pattern you see in the scatterplot, as well as any deviations from that pattern.
(b) If field and laboratory measurements all agree, then the points should fall on the line drawn on the plot, except for small variations in the measurements. Is this the case? Explain.
(c) The line drawn on the scatterplot is not the least-squares regression line. How would the slope and intercept of the least-squares line compare? Justify your answer.
The risks of obesity A study observes a large group of people over a -year period. The goal is to see if overweight and obese people are more likely to die during the study than people who weigh less. Such studies can be misleading because obese people are more likely to be inactive
and poor.
(a) What are the explanatory and response variables in the study?
(b) If the study finds a strong association between these variables, can we conclude that increased
weight causes a greater risk of dying? Why or why not?
The graph at the top right plots the gas mileage (miles per gallon) of various cars from the same model year versus the weight of these cars in thousands of pounds. The points marked with red dots correspond to cars made in Japan. From this plot, we may conclude that
(a) there is a positive association between weight and gas mileage for Japanese cars.
(b) the correlation between weight and gas mileage for all the cars is close to .
(c) there is little difference between Japanese cars and cars made in other countries.
(d) Japanese cars tend to be lighter in weight than other cars.
(e) Japanese cars tend to get worse gas mileage than other cars.
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