1. A right-tailed test: z = 2.38. Determine the P-value.

2. A two-tailed test: z = 1.31. Determine the P-value.

3. A left-tailed test: z = -0.58. Determine the P-value.

4. For a two-tailed test at 86.12% confidence, Z =

5. For a one-tailed test (lower tail) at 93.7% confidence, Z =

6. A one-tailed test (upper tail) at 87.7% confidence; Z =

7. A random sample of 225 workers taken from the management level of a multinational corporation

gives a mean annual salary of 100,000 with a standard deviation of 10000. What is the 95%

confidence interval for the population mean?

8. A wine shop owner wishes to estimate the mean number of bottles sold to account holders per month

(). A sample of 60 accounts gives a sample mean ( ) of 8.6 bottles per month with a sample

standard deviation (s) of 2.3.

a. Develop a 95% confidence interval for the population mean.

b. Develop a 99% confidence interval for the population mean.

c. How would the 99% confidence interval change if the same sample mean and standard

deviation were obtained from a sample of 100 accounts?

9. In the past, the mean running time for a certain type of flashlight battery has been 9.6 hours. The

manufacturer has introduced a change in the production method and wants to perform a hypothesis

test to determine whether the mean running time has changed as a result. Determine the null and

alternative hypotheses.

10. The owner of a football team claims that the average attendance at games is over 81,100, and he is

therefore justified in moving the team to a city with a larger stadium. Determine the null and

alternative hypotheses.

11. A pharmaceutical company has a new drug which relieves headaches. However, there is some

indication that the drug may have the side effect of increasing blood pressure. Determine the null and

alternative hypotheses.

12. A health insurer has determined that the "reasonable and customary" fee for a certain medical

procedure is 1200. They suspect that the average fee charged by one particular clinic for this

procedure is higher than 1200. The insurer wants to perform a hypothesis test to determine whether

their suspicion is correct. Classify the hypothesis test as two-tailed, left-tailed, or right-tailed.

13. A machine fills packets with spice which are supposed to have a mean of 40 grams. A random

sample of 36 packets is taken to test this hypothesis and the mean weight is found to be 42.4 grams

with a standard deviation of 6 grams. Is this weight consistent with the hypothesised mean at the 5%

level of significance?

14. Assume the same data in the previous example. Test to see whether the mean is statistically greater

than 40 grams at the 1% level of significance.

15. According to the T-Table provided, for two tailed test, the t value with a 95% confidence and 24

degrees of freedom is

16. For a one-tailed test (upper tail), a sample size of 18 at 95% confidence, t is

17. For a one-tailed test (lower tail), a sample size of 10 at 90% confidence, t is

18. James Watts, the investment executive, claims that the average yearly rate of return on the stocks he

recommends is less than 10.0%. His team wants to perform a hypothesis test to determine whether

his suspicion is correct, the correct set of hypotheses is

19. A soft drink filling machine, when in perfect adjustment, fills the bottles with 12 ounces of soft drink.

Any over-filling or under-filling results in the shutdown and readjustment of the machine. To

determine whether or not the machine is properly adjusted, the correct set of hypotheses is

20. The average life expectancy of tires produced by the Whitney Tire Company has been 40,000 miles.

Management believes that due to a new production process, the life expectancy of their tires has

increased. In order to test the validity of their belief, the correct set of hypotheses is

21. A machine fills packets with spice which are supposed to have a mean of 40 grams. A random

sample of 25 packets is taken to test this hypothesis and the mean weight is found to be 42.4 grams

with a standard deviation of 5 grams. Is this weight consistent with the hypothesised mean at the 5%

level of significance?

22. Assume the same data in the previous example. Test to see whether the mean is statistically greater

than 40 grams at the 1% level of significance.

23. A firm is concerned that the amount of chemicals being provided to them is less than that being

claimed by the supplier. The supplier claims that there is an average of 50 grams of the

corresponding chemical in sacks being provided by them. After taking a random sample of 8 sacks

the customer find a mean of 49.2 grams with a standard deviation of 1.6grams. Test to see if their

concern is justified at the 5% level of significance.

24. Use a significance level of 0.05 to test the claim that = 19.6. The sample data consists of 10 scores

for which x = 20.1 and standard deviation = 4.1. State the null and alternative hypotheses, compute

the value of the test statistic, and find the P-value for the sample. State your conclusions about the

claim.

25. In tests of a computer component, it is found that the mean time between failures is 520 hours. A

modification is made which is supposed to increase the time between failures. Tests on a random

sample of 10 modified components resulted the mean of 537.1 hours and standard deviation is 20.7

hours.At the 0.05 significance level, test the claim that for the modified components, the mean time between

failures is greater than 520 hours.