# Μ 1 μ 2 11 a number of students in a grade 9 maths

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( μ 1 μ 2 ) 11. A number of students in a Grade 9 maths course at a particular high school were randomly divided into two groups. The experimental group received teaching according to the new curriculum while the control group did not. All the students were given a test of computational skill (out of a total of 5 points) after the course and the results were as follows: for the experimental group, the sample size was 27, the sample mean was 1.19 and the sample variance was 74. For the control group, the sample size was 25, the sample mean was 3.54 and the sample variance was 80. Assume that population variances are equal. Construct a 99% confidence interval for the difference between the population mean test scores of the new and old curriculums. ( μ 1 μ 2 ) 12. A mail-order company has two warehouses, one on the West Cost and one on the East Coast. The policy of the company is to mail all orders placed with it within 48 hrs. A recently taken sample of 450 orders placed with the warehouse on the West Coast showed that 370 of them mailed within 48 hrs. Another sample of 370 orders placed with the warehouse on the East Coast showed 280 of them were mailed within 48 hrs. Construct a 90% confidence interval for the difference between the population proportions. ( p 1 p 2 ) 13. A beer company wants to determine whether a different marketing strategy is needed for their national market as compared with their marketing strategy for their international market. One of their best beers is tasted and tested both national and international. A sample of 400 national beer drinkers showed that 60% liked the beer.