in the hanes sample, the average height of the boys was 136 cm at age 9 and 146 cm at age 11. At age 11, the average of all the children was 147 cm. On the average, are boys taller than girls at age 11?
No. if the average boy height at age 11 is 146cm, and the average overall height at age 11 is 147cm, the average girl height must be greater than the average boy height. In this instance the average girl height at age 11 is 148cm.