Table 2.5 (page 109) gives data on the true calories in 10 foodsand the average guesses made by a large group of people. Exercise2.26 explored the influence of two outlying observations on thecorrelation.
(a) Make a scatterplot suitable for predicting guessed caloriesfrom true calories. Circle the points for spaghetti and snack cakeon your plot. These points lie outside the linear pattern of theother 8 points.
(b) Find the least-squares regression line of guessed calorieson true calories. Do this twice, first for all 10 data points andthen leaving out spaghetti and snack cake.
(c) Plot both lines on your graph. (Make one dashed so you cantell them apart.) Are spaghetti and snack cake, taken together,influential observations? Explain your answer.
Table 2.5
| Guessed | Correct |
Food | calories | calories |
8 oz. whole milk | 196 | 159 |
5 oz. spaghetti with tomato sauce | 394 | 163 |
5 oz. macaroni with cheese | 350 | 269 |
One slice wheat bread | 117 | 61 |
One slice white bread | 136 | 76 |
2-oz. candy bar | 364 | 260 |
Saltine cracker | 74 | 12 |
Medium-size apple | 107 | 80 |
Medium-size potato | 160 | 88 |
Cream-filled snack cake | 419 | 160 |
