Question: Heights of children who repeat grades. Are children who repeat a grade in elementary school shorter on average than their peers? To answer this question, researchers compared the heights of Australian schoolchildren who repeated a grade to those who did not (Archives of Disease in Childhood, April 2000). All height measurements were standardized using z-scores. A summary of the results, by gender, is shown in the table on p. 77.
(a) Conduct a test of hypothesis to determine whether the average height of Australian boys who repeated a grade is less than the average height of boys who never repeated. Use α = .05.
(b) Repeat part a for Australian girls.
(c) Summarize the results of the hypothesis tests in the words of the problem.
