Refer Exercise 12.35 Fit a single model to the data that will relate x, the soil mercury content. To y, the plant mercury contents, with separate intercepts and slopes for the three crops.
a. Does there appear to be a difference in slopes for the three crops?
b. Does there appear to be a difference in intercepts for the three crops?
c. Does a first-order model appear to provide an adequate fit to the data?
In exercise

Type of Crop MerCon Corn Wheat Barley 133.3 25.8 24.6 15.1 18.0 174 92 10.0 259 8.6 1 231 9. 45 82 2 314 35.7 145 409 22.9 105 34.6 234 184 24.9 21. 4.3 9.6 6.4 23.2 3 404 352 52.1 307 46.9 27 135 303 19.3 336 308 22.0 12.9 35 27.9 4 65.6 74.7 77.3 64.2 713 50.6 53.9 552 48.6 352 36.6 34 68 27.7 39.5 5 94.4 949 88. 100.1 1048 849 77.6 933 643 742 56.7 42.8 49.0 47.9 45.2 6 1234 158.6 137.3 1567 1335 1075 919 87.7 106.2 108. 708 75.7 100.3 64.6 70.1 1