Figure 4:
Based on gender, I wanted to test if there was a difference in the proportions of the mean scale score of the boys and girls of the schools having higher than average mean scale score which have outlets with lead levels > 15 ppb. For this I performed the Chi-squared test.

H0 : There is no difference in the proportion of boys of the schools with mean scale score greater than the average score and the proportion of girls with mean scale score greater than the average score of the schools having > 0 high lead water levels . significance level,alpha=0.05

H1 : There is a difference in the proportion of boys of the schools with mean scale score greater than the average score and the proportion of girls with mean scale score greater than the average score of the schools having > 0 high lead water levels .