Question

The weights of newborns at a hospital have an average of 7 lb and an SD of 1.2 lb. The average head circumference of the newborns is 14 inches and the SD is 0.5 inches. The correlation between the two variables is 0.55 and the scatter diagram is football shaped. The regression line for estimating head circumference based on weight is drawn on the scatter diagram, with weight on the horizontal axis.

1. For about 50% of the newborns, the regression estimate of head circumference based on weight is correct to within _____________ inches.