Chapter 4: Problem 47
Briefly explain why a large value of \(r^{2}\) is desirable in a regression setting.
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Chapter 4: Problem 47
Briefly explain why a large value of \(r^{2}\) is desirable in a regression setting.
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The paper "School Achievement Strongly Predicts Midlife IQ" (Intelligence [2007]: \(563-567\) ) examined the relationship between school achievement test scores in grades 3 to 8 and IQ measured many years later. The authors reported an association between school achievement test score and midlife IQ, with a correlation coefficient of \(r=0.64\) a. Interpret the value of the correlation coefficient. b. A science writer commenting on this paper (Livescience, April 16,2007\()\) said that the correlation between school achievement test scores and IQ was very strong - even stronger than the correlation between height and weight in adults. Which of the following values for correlation between height and weight in adults is consistent with this statement? Justify your choice. \(\begin{array}{lllll}r=-0.8 & r=-0.3 & r=0.0 & r=0.6 & r=0.8\end{array}\)
For a given data set, the sum of squared deviations from the line \(y=40+6 x\) is \(529.5 .\) For this same data set, which of the following could be the sum of squared deviations from the least squares regression line? Explain your choice. i. 308.6 ii. 529.6 iii. 617.4
The paper "Digit Ratio as an Indicator of Numeracy Relative to Literacy in 7-Year-Old British Schoolchildren" (British Journal of Psychology [2008]: \(75-85\) ) investigated a possible relationship between \(x=\) digit ratio (the ratio of the length of the second finger to the length of the fourth finger) and \(y=\) difference between numeracy score and literacy score on a national assessment. (The digit ratio is thought to be inversely related to the level of prenatal testosterone exposure.) The authors concluded that children with smaller digit ratios tended to have larger differences in test scores, meaning that they tended to have a higher numeracy score than literacy score. This conclusion was based on a correlation coefficient of \(r=-0.22 .\) Does the value of the correlation coefficient indicate that there is a strong linear relationship? Explain why or why not.
Draw two scatterplots, one for which \(r=1\) and a second for which \(r=-1\).
Data on \(y=\) time to complete a task (in minutes) and \(x=\) number of hours of sleep on previous night were used to find the least squares regression line. The equation of the line was \(\hat{y}=12-0.36 x .\) For this data set, would the sum of squared deviations from the line \(y=12.5-0.5 x\) be larger or smaller than the sum of squared deviations from the least squares regression line? Explain your choice. (Hint: Think about the definition of the least- squares regression line.)
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