1.If the difference between the hypothesized population mean and the mean of the sample is large, we ___ the null hypothesis. If the difference between the hypothesized population mean and the mean of the sample is small, we ___ the null hypothesis.

2. At the Chrysler manufacturing plant, there is a part that is supposed to weigh precisely 19 pounds. The engineers take a sample of parts and want to know if they meet the weight specifications. What are our null and alternative hypotheses?

3. In a hypothesis test, if difference between the sample mean and the hypothesized mean

by the standard error falls in the middle of the distribution and in between the critical values, we ___ the null hypothesis. If this number falls in the critical regions and beyond the critical values, we ___ the null hypothesis.

4. Sacramento County high school seniors have an average SAT score of 1,020. From a random sample of 144 Sacramento High School students we find the average SAT score to be 1,100 with a standard deviation of 144: We want to know if these high school students are representative of the overall population. What are our hypotheses?

5. A researcher claims that black horses are, on average, more than 30 lbs heavier than white horses, which average 1100 lbs. What is the null hypothesis, and what kind of test is this?

6. What is the critical value Z for a 95% confidence level, assuming a two-tailed test?

7. What would be the critical value for a right-tailed test with a = 0:01?

8 and 9. For each question:

a) State the null and alternative hypothesis for a test to determine the validity of the claim

b) Identify left, right, or two-tailed test type

#1. The average Siberian Husky weighs more than 35 pounds.

#2. The United Parcel Service claims less than 5-day shipping times for ground packages.

10. In a study on the effects of exercise on stress, researchers predict simply that there will be a difference in stress levels between the exercise and no exercise groups. The researchers are using _____.

a. a two-tailed hypothesis

b. a directional hypothesis

c. a one-tailed hypothesis

d. both directional and one-tailed hypotheses

11. A researcher is interested in whether students who play sports have a higher or lower body mass index (BMI) than students in the general population. The researcher is unsure whether playing sports will decrease body mass (due to more calories burned) or increase body mass (due to more muscle mass). This is a _____-tailed test and the zcv is _____.

a. two; 1.96

b. one; 1.65

c. two; 1.65

d. one; 1.96

12. A researcher is interested in whether students who are musicians have higher intelligence test scores than students in the general population. The researcher predicts that playing a musical instrument is associated with higher intelligence test scores. The researcher selects a sample of 75 musicians from local high schools and gives them an intelligence test. The mean for the sample is 105. The mean for the general population () is 100 with a standard deviation () of 15. What is zobt for this sample?

a. .33

b. 1.89

c. 2.89

d. 3.25

13. A researcher is interested in whether high school students who play sports have a higher or lower body mass index (BMI) than students in the general population. The researcher is unsure whether playing sports will decrease body mass (due to more calories burned) or increase body mass (due to more muscle mass). The researcher selects a sample of 60 athletes and finds that their average BMI is 22. The average () in the general population of students is 22.5 with a standard deviation () of 3. What is zobt for this sample?

a. .98

b. 1.29

c. 1.96

d. 2.25

14. Given: For one section of the SAT: = 500 and = 100. The SAT was given to a sample of N = 35 and the mean SAT for this sample was 536. Calculate the z test for this sample mean. Does this sample differ significantly from the population for a two-tailed test? (3 points)

Questions 15-19 are two points each

15. Imagine that you conducted a single-sample t test with 12 subjects. For a two-tailed test, the tcv at = .05 would be:

a. 1.796.

b. 2.074.

c. 2.179.

d. 2.201.

16. Imagine that you conducted a single-sample t test with 15 subjects. For a one-tailed test, the tcv at = .05 would be:

a. 1.761.

b. 1.753.

c. 2.179.

d. 2.201.

17. If a researcher reported for a one-tailed single-sample t test that t(10) = 1.96, then:

a. p < .02.

b. p < .05.

c. p < .01.

d. p < .001.

18. The null hypothesis for a two-tailed independent-groups t test states that:

a. H0: 1 2.

b. H0: 1 = 2.

c. Ha: 1 2.

d. Ha: 1 = 2.

19. If an independent-groups t test has 13 subjects in each group, then the degrees of freedom are:

a. 26.

b. 24.

c. 13.

d. 12.

20. This is a big one!!! (15 points)

T-tests

A research study was conducted to examine the differences between older and younger adults on perceived life satisfaction. A pilot study was conducted to examine this hypothesis. Ten older adults (over the age of 70) and ten younger adults (between 20 and 30) were give a life satisfaction test (known to have high reliability and validity). Scores on the measure range from 0 to 60 with high scores indicative of high life satisfaction; low scores indicative of low life satisfaction. The data are presented below. Compute the appropriate t-test and answer all questions.

Older Adults Younger Adults

45 34

38 22

52 15

48 27

25 37

39 41

51 24

46 19

55 26

46 36

Mean = 44.5 Mean = 28.1

S = 8.682677518 S = 8.543353492

S2 = 75.388888888 S2 = 72.988888888

Independent t-test

1. What is your computed answer? tobs =

2. What would be the null hypothesis in this study?

3. What would be the alternate hypothesis?

4. What probability level did you choose and why?

5. What is your tcrit? tcrit =

6. Is there a significant difference between the two groups?

7. Interpret your answer.

8. If you have made an error, would it be a Type I or a Type II error? Explain your answer.