More than one million motorcycles are sold annually (www.webbikeworld.com). Off-road motorcycles (often called dirt bikes) are a

More than one million motorcycles are sold annually (www.webbikeworld.com). Off-road motorcycles (often called €œdirt bikes€) are a market segment (about 18%) that is highly specialized and offers great variation in features. This makes it a good segment to study to learn about which features account for the cost (manufacturer€™s suggested retail price, MSRP) of a dirt bike. Researchers collected data on 2005 model dirt bikes (lib.stat.cmu.edu/datasets/dirtbike_aug.csv). Their original goal was to study market differentiation among brands (The Dirt on Bikes: An Illustration of CART Models for Brand Differentiation, Jiang Lu, Joseph B. Kadane, and Peter Boatwright, server1.tepper.cmu.edu/gsiadoc/WP/2006-E57.pdf), but we can use these to predict msrp from other variables. Here are scatterplots of three potential predictors, Wheelbase (in), Displacement (cu in), and Bore (in).

Comment on the appropriateness of using these variables as predictors on the basis of the scatterplots.

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8000 6000 4000 2000 37.5 45.0 525 Wheelbase 8000 6000 4000 2000 125 250 375 500 Displacement 8000 6000 4000 2000 50.0 75.0