Question

Health Promotion It is fairly well known that perception of weight by adoles- cents does not always agree with actual weight. What is less clear is whether perception of weight differs by gender. For this purpose, a study was performed among students in a local high school, where students provided their actual height and weight by self-report. The following data were obtained from 286 students (143 boys and 143 girls). (The data for this problem were provided by Laura Rosner.) he students were classified as underweight if their body- mass index (BMI) (kg/m2) was less than 18.0 kg/m2, as normal if their BMI was 2 18.0 and< 25.0, and overweight if their BMI was 2 25.0. Based on these criteria, 17 of the girls were underweight, 113 were of normal weight, and 13 were overweight. For the boys, 7 were underweight, 115 were of normal weight, and 21 were overweight. 10.97What test procedure can be used to assess whether the weight status of boys significantly differs from girls? 10.98 Perform the test procedure in Problem 10.97, and provide a two-tailed p-value.

Answer 1

10.97
chi-square test of independence can be used to assess this

10.98

		c1	c2	c3	sum
	r1	17	113	13	143
	r2	7	115	21	143
	sum	24	228	34	286
	Eij	1	2	3
expected	1	12	114	17
	2	12	114	17
	0i	17	113	13	7	115	21
	Ei	12	114	17	12	114	17
								sum
	(Oi-Ei)^2/Ei	2.083333	0.008772	0.941176	2.083333	0.008772	0.941176471	6.066563
							critical value	5.991465
							p-value	0.048157

since TS = 6.066563 > 5.99 (critical value at 0.05 level)

p-value = 0.048

we reject the null hypothesis