Question

The data for comparing two sample proportions can be presented in a two-way table containing the counts of successes and failures in both samples, with two rows and two columns. In Exercise 23.2, a survey of the consequences of video-gaming on 14- to 18-year-olds is described. Another question from the survey was about aggressive behavior as evidenced by getting into serious fights, and the comparison was between girls that have and have not played video games. Here are the data:

	Serious Fights-Yes	Serious Fights-No
Played games	36	55
Never played games	578	1436

Is there evidence that the proportions of 14- to 18-year-old girls who have or have not gotten into serious fights differ between those who have played or never have played video games? Find the chi-square statistic x² and its P-value.

Answer 1

Ans:

	Observed(fo)
	Yes	No	Total
Played games	36	55	91
Never played games	578	1436	2014
Total	614	1491	2105
	Expected(fe)
	Yes	No	Total
Played games	26.54	64.46	91
Never played games	587.46	1426.54	2014
Total	614	1491	2105
	Chi square=(fo-fe)^2/fe
	Yes	No	Total
Played games	3.37	1.39	4.76
Never played games	0.15	0.06	0.21
Total	3.52	1.45	4.97

Test statistic:

Chi square=4.97

df=(2-1)*(2-1)=1

p-value=CHIDIST(4.97,1)=0.0258