Reference no: EM132399713

1. Suspecting that television repair shops tend to charge women and men differently, Emily disconnected the speaker wire on her portable television and took it to a sample of 12 shops. She was given repair estimates that averaged $85, with a standard deviation of $28. Her friend John, taking the same set to another sample of 9 shops, was provided with an average estimate of $65, with a standard deviation of $21. Assuming normal populations with equal variances, use the 95% confidence level in evaluating Emily's suspicion.

2. The developer of a new welding rod claims that spot welds using his product will have greater strength than conventional welds. For 45 welds using the new rod, the average tensile strength is 23,500 pounds per square inch, with a standard deviation of 600 pounds. For 40 conventional welds on the same materials, the average tensile strength is 23,140 pounds per square inch, with a standard deviation of 750 pounds. Use the 0.01 level in testing the claim of superiority for the new rod. Using the appropriate statistical table, what is the approximate p-value for this test? Conduct a two-tailed test and then see what you find.

3. Independent random samples of vehicles traveling past a given point on an interstate highway have been observed on Monday versus Friday. For 16 cars observed on Monday, the average speed was 59.4 mph, with a standard deviation of 3.7 mph. For 20 cars observed on Friday, the average speed was 56.3 mph, with a standard deviation of 4.4 mph. Following the common sense and assuming normal populations, can we conclude, at the 0.05 level, that the average speed for all vehicles was slower on Friday than on Monday?

4. For a sample of 48 finance majors, the average time spent reading each issue of the campus newspaper is 19.7 minutes, with a standard deviation of 7.3 minutes. The corresponding figures for a sample of 40 management information system majors are 16.3 and 4.1 minutes. Using the 0.01 level of significance, test the null hypothesis that there is no difference between the two groups on time they spend reading each issue of campus newspaper.

5. Two training programs have been introduced to improve students' writing skills. For 250 students participating in Program A, 130 showed improvement; for another group of 200 students selecting Program B, 128 demonstrated improved writing. At the 0.05 level, is it feasible to conclude one program is superior to the other?