On average, do people gain weight as they age? Using data from the same study as in Exercise 11-1, we provide some summary statistics for both age and weight.

(a) Calculate the least squares estimates of the slope and intercept. Graph the regression line.

(b) Use the equation of the fitted line to predict the weight that would be observed, on average, for a man who is 25 years old.

(c) Suppose that the observed weight of a 25-year-old man is 170 lbs. Find the residual for that observation.

(d) Was the prediction for the 25-year-old in part (c) an overestimate or underestimate? Explain briefly.

TABLE 11-1 NFL Data

ix = 543503.00 =11211.00 i=l Ey = 8110405.02 Ey = 44520.80 i=1 i=1 Ex;y; = 1996904.15 i=1 Yards per Attempt Rating Points Player Team Philip Rivers SD 8.39 105.5 Chad Pennington MIA 7.67 97.4 Kurt Warner ARI 7.66 96.9 Drew Brees NO 7.98 96.2 Peyton Manning IND 7.21 95 Aaron Rodgers GB 7.53 93.8 Matt Schaub HOU 8.01 92.7 Tony Romo DAL 7.66 91.4 Jeff Garcia TB 7.21 90.2 Matt Cassel NE 7.16 89.4 Matt Ryan ATL 7.93 87.7 Shaun Hill SF 7.10 87.5 Seneca Wallace SEA 6.33 87 Eli Manning NYG 6.76 86.4 Donovan McNabb PHI 6.86 86.4 Jay Cutler DEN 7.35 86 Trent Edwards BUF 7.22 85.4 Jake Delhomme CAR 7.94 84.7 Jason Campbell WAS 6.41 84.3 David Garrard JAC 6.77 81.7 Brett Favre NYJ 6.65 81 Joe Flacco BAL 6.94 80.3 Kerry Collins TEN 6.45 80.2 Roethlis- berger Ben PIT 7.04 80.1 Kyle Orton CHI 6.39 79.6 JaMarcus Russell OAK 6.58 77.1 Tyler Thigpen KC 6.21 76 Gus Freotte MIN 7.17 73.7 Dan Orlovsky DET 6.34 72.6 Marc Bulger STL 6.18 71.4 Ryan Fitzpatrick CIN 5.12 70 Derek Anderson CLE 5.71 66.5