1. A teacher is considering replacing the current video he uses to introduce students to the basics of economics with a new video. Students are randomly assigned to two groups, and they all take the same written exam after watching the video. If the students who view the new video score higher, the teacher will switch to the new video; otherwise, he will continue with the current video. The results of the tests are summarized below.

Current Video: n₁ = 26 ₁ = 77.1 S₁ = 7.8

New Video: n₂ = 26 ₂ = 80.0 S₂ = 8.1

Assuming equal population standard deviations, determine what the teacher should do at = 0.10.

2. To compare customer satisfaction levels of two competing cable television companies,100customers of CompanyAand100customers of CompanyBwere randomly selected and were asked to rate their cable companies on a five-point scale, with1being least satisfied and5most satisfied. The survey results are given below:

Company A: mean rating = 3.51, with a standard deviation of 0.51.

Company B: mean rating = 3.24, with a standard deviation of 0.52.

At = 0.05, is there a difference in average satisfaction levels of customers of the two companies as measured on this five-point scale?

3. You are a financial analyst and want to determine if there a difference in dividend yield (in %) between stocks listed on the NYSE & the NASDAQ. A sample of 26 stocks listed on the NYSE shows a mean yield of 3.25 and a standard deviation of 1.30. A sample of 26 stocks listed on the NASDAQ shows a mean yield of 2.75 and a standard deviation 0f 1.15. At = 0.05, is there a difference in average dividend yield?

4. A study conducted by Starbucks found that people aged 25 to 49 drank an average of 2.25 cups of coffee per day and that those aged 50 and over drank an average of 2.00 cups per day. The two groups show, respectively, sample sizes of 200 and 100 and sample standard deviations of 0.5 and 0.7. Test at a significance level of 0.10 whether people aged 25 to 49 in general drink more coffee than those aged 50 and over.