Answer:
The average height difference between randomly selected girls and boys is 5.5 inches. The standard deviation of the difference in height is about 4.18808 inches.
Step-by-step explanation:
Just subtract the girls' average from the boys' average to find the average difference between any girl and boy.
Calculate the variance from the given standard deviations (square the SD). Add the variances and find the square root of that sum. (SD = square root of Var).
The standard deviation is only able to be calculated when the two variables are independent.
The variances are added and not subtracted because finding a different average doesn't mean that the data that is being observed also has a different deviation (also there isn't really a situation where you would subtract the Var).
