Babsie is a public affairs specialist at Park University A p

Babsie is a public affairs specialist at Park University. A press release issued by Babsie based on some research claims that Park University students study at least as much as the national average for students at four year universities. Across the nation, 73 percent of all students at four year universities study at least four hours per week. Seventy percent of one hundred randomly selected Park University students surveyed claimed to study more than four hours per week. Should the University retract its previous statement? Explain why or why not. Answer using a 95 percent confidence interval.

Solution

Sample proportion phat = 0.7 Varaince of proportion = p*(1-p)/n = 0.7(0.3)/100 =0.0021 S.D. of p is 0.0458 Confidence limits: phat-zval*sd = 0.7 - (1.96)(0.045826) phat-zval*sd = 0.7 + (1.96)(0.045826) Confidence limits are ( 0.6102 , 0.7898 ) No, the university should not retract its previous statement. The interval includes 0.73 as well as 0.70. If you had conducted a test of hypothesis of 0.73 versus 0.70, it would have concluded that there was no significant difference between 0.73 and 0.70.