In the Christmas tree survey, respondents who had a tree during the holiday season were asked whether the tree was natural or artificial. Respondents were also asked if they lived in an urban area or in a rural area. Of the 420 households displaying a Christmas tree, 160 lived in rural areas and 260 were urban residents. The tree growers want to know if there is a difference in preference for natural trees versus artificial trees between urban and rural households. Here are the data:.
Population n X (natural)
1(rural) 150 60
2(urban) 250 90
Find 95% Confidence interval for rural and urban proportions difference.