TEST of Hypothesis

1. DEWA (Dubai electricity and Water authority) wants to compare consumption of electricity during the summer season in Jumeirah and Mirdif. For each household sampled, the monthly electricity bill is recorded with the following results: ( use 5 % level of significance)

Jumeirah Mirdif

525 dhs 500 dhs

50 dhs 75 dhs

25 21

a. Is there evidence that the mean electricity bill in Jumeirah is above 500 dhs?

b. Is there evidence that the mean electricity bill in Jumeirah is more than the mean electricity bill in Mirdif?

2. A researcher at the University of Michigan medical school believes that coffee consumption may increase the heart beat rate. Suppose it is known that the heart beat rate is normally distributed with an average of 70 for adults. A random sample of 25 adults was selected and it was found that their average heartbeat was 73 after coffee consumption, with a standard deviation of 7. a. Formulate the null and alternative hypothesis.b. Test the hypotheses in part (a) at the 10% significance level to determine if we can

infer that coffee consumption increases the heart beat rate.

3. According to a Louis Harris poll, 63% of men drivers always use seat belts. A recent sample of 900 men drivers showed that 60% of them always use seat belts. Test at the 1% significance level if the proportion of men drivers who always use seat belts is less than 0.63.

4. A random sample of 24 college students was asked how much time they spent watching television on a week day. The mean response was 148 minutes. and the standard deviation was 48 minutes. Assume that population values are normally distributed, and test the hypothesis at 0.01 level, that the population mean time is more than 120 minutes.

5. A department store management claims that at least 45% of persons who visit this store make a purchase. In a sample of 400 persons who visited this store, 37% made a purchase. Test at the 5% significance level if the claim of the management is true.

6. A market analyst is interested to know the difference in percentages between owners of Ford and Chevrolet cars who are happy with their purchase. He samples 250 Ford owners and finds that 130 are happy with their purchase. Similarly, he samples 200 Chevy owners and finds that 105 are happy with their purchase. Test at 5% level that Ford owners are happier than Chevy owners?

7. Independent random samples taken on two university campuses revealed the following information concerning the average amount of money spent on textbooks during the fall semester.

University A University B

Sample Size 50 40

Average Purchase $280 $250

Standard Deviation $20 $23

At = .05, test to determine if, on the average, students at University A spend more on textbooks then the students at University B