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Chapter 3: Q.1.4 (page 167)
Should you use this line to predict the rat鈥檚 weight at age years? Use the equation to make the prediction and think about the reasonableness of the result. (There aregrams in a pound.)
No, it cannot be used for predictions. Because the weight of a newborn is not possible for a rat.
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Predict the rat鈥檚 weight after weeks. Show your work
Joan is concerned about the amount of energy she uses to heat her home. The graph below plots the mean number of cubic feet of gas per day that Joan used each month against the average temperature that month (in degrees Fahrenheit) for one heating season.
(a) Does the plot show a positive or negative association between the variables? Why does this make sense?
(b) What is the form of the relationship? Is it very strong? Explain your answers.
(c) Explain what the point at the bottom right of the plot represents.
Southern education For a long time, the South has lagged behind the rest of the United States in the performance of its schools. Efforts to improve education have reduced the gap. We wonder if the South stands out in our study of state average SAT Math scores.
The figure below enhances the scatterplot in Figure (page ) by plotting southern states in red.
(a) What does the graph suggest about the southern states?
(b) The point for West Virginia is labeled in the graph. Explain how this state is an outlier.
A government report looked at the amount borrowed for college by students who graduated in and had taken out student loans.12 The mean amount was and the standard deviation was . The median wasand the quartiles were and
(a) Compare the mean and the median. Also compare the distances of Q1 and Q3 from the median. Explain why both comparisons suggest that the distribution is right-skewed.
(b) The right-skew pulls the standard deviation up. So a Normal distribution with the same mean and standard deviation would have a third quartile larger than the actual Q3.Find the third quartile of the Normal distribution withand and compare it with.
Airlines have increasingly outsourced the maintenance of their planes to other companies. Critics say that the maintenance may be less carefully done so outsourcing creates a safety hazard. As evidence, they point to government data on the percent of major maintenance outsourced and the percent of flight delays blamed on the airline (often due to maintenance problems): Make a scatterplot by hand that shows how delays relate to outsourcing.
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