Chapter 13.3, Problem 23PB

Does leg press help predict body strength? Chapter 12 analyzed strength data for 57 female high school athletes. Upper body strength was summarized by the maximum number of pounds the athlete could bench press (denoted maxBP). This was predicted well by the number of times she could do a 60-pound bench press (denoted BP60). Can we predict maxBP even better if we also know how many times an athlete can perform a 200-pound leg press? The table shows results after adding this second predictor (denoted LP200) to the model.

1. a. Does LP200 have a significant effect on maxBP if BP60 is also in the model? Show all steps of a significance test to answer this.
2. b. Show that the 95% confidence interval for the slope for LP200 equals 0.21 ± 0.30, roughly (−0.1, 0.5). Based on this interval, does LP200 seem to have a strong impact, or a weak impact, on predicting maxBP if BP60 is also in the model?
3. c. Given that LP200 is in the model, provide evidence from a significance test that shows why it does help to add BP60 to the model.