=+13.46 A regression of y 5 sunburn index for a pea plant on x 5 distance from an ultraviolet light source was considered in Exercise 13.22. The data and summary statistics presented there give a x 2 5 155,400 a y 2 5 24,869.33 a xy 5 57,760 n 5 15 a x 5 1350 a y 5 600 a y 2 5 7745 a x 2 5 190.78 a x 5 269 a y 5 51 a xy 5 1081.5