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Chapter 3: Q.30 (page 163)
If women always married men who were years older than themselves, what would the correlation between the ages of husband and wife be?
(a) (c) (e) Can鈥檛 tell without
(b) (d) seeing the data
The correlation between the ages of husband and wife be .
The answer is Option (b)
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Beavers and beetles Do beavers benefit beetles? Researchers laid out circular plots, each meters in diameter, in an area where beavers were cutting down cottonwood trees. In each plot, they counted the number of stumps from trees cut by beavers and the number of clusters of beetle larvae. Ecologists think that the new sprouts from stumps are more tender than other cottonwood growth, so beetles prefer them. If so, more stumps should produce more beetle larvae. Here are the data:
How sensitive to changes in water temperature are coral reefs? To find out, measure the growth of corals in aquariums where the water temperature is controlled at different levels. Growth is measured by weighing the coral before and after the experiment. What are the explanatory and response variables? Are they categorical or quantitative?
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.
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.
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?
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