(Solution) - Several quantitative variables were recorded for each in a sample -(2025 Original AI-Free Solution)

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Several quantitative variables were recorded for each in a sample of 28 geography journals: cost of a 1-year subscription (dollars); Journal Impact Factor (JIF) - the average number of times articles from the journal have been cited; number of citations for the journal over the past 5 years; and Relative Price Index (RPI). The data for the 28 journals are saved in the file. (Selected observations are listed below.)

a. Fit a straight-line model relating cost (y) to JIF (x). Find an estimate of ?, the standard deviation of the error term, and interpret its value.
b. Fit a straight-line model relating cost (y) to number of citations (x). Find an estimate of ?, the standard deviation of the error term, and interpret its value.
c. Fit a straight-line model relating cost (y) to RPI (x). Find an estimate of ?, the standard deviation of the error term, and interpret its value.
d. Which predictor of cost-JIF, number of citations, or RPI-leads to a regression line with the smallest errors of prediction?
For Information: Refer to the Geoforum (Vol. 37. 2006) study of whether the price of a geography journal is correlated with quality. Exercise 2.127.