**Assignment** **3**

**Statistics Exercise II: Statistical inference, 1- and 2-sample t-tests**

**These weekly exercises provide the opportunity for you to understand and apply statistical methods and analysis. Unless otherwise stated, use 5% (.05) as your alpha level (cutoff for statistical significance).**

**#1. ** Define “power” in relation to hypothesis testing.

**#2. ** Alpha (a) is used to measure the error for decisions concerning true null hypotheses. What is beta (ß) error used to measure?

**#3. ** In the following studies, state whether you would use a one-sample *t* test or a two-independent-sample *t* test.

- A study testing whether night-shift workers sleep the recommended 8 hours per day
- A study measuring differences in attitudes about morality among Democrats and Republicans
- An experiment measuring differences in brain activity among rats placed on either a continuous or an intermittent reward schedule

**Use SPSS and the data file found in syllabus resources (DATA540.SAV) to answer the following questions. Round your answers to the nearest dollar, percentage point, or whole number. **

**#4. ** Test the age of the participants (AGE1) against the null hypothesis H0 = 34. Use a one-sample t-test. How would you report the results?

a. *t* = -1.862, *df* = 399, *p* > .05

b. *t* = -1.862, *df* = 399, *p* < .05

c. *t* = 1.645, *df* = 399, *p* > .05

d. *t* = 1.645, *df* = 399, *p* < .05

**#5. ** What is the mean and standard deviation for the Lifestyle score (L)?

a. 31.22, 7.99

b. 36.19, 8.54

c. 30.03, 7.28

d. 55, 13

**#6. ** The first case shown in the data file is a firefighter with a financial Risk-Taking score (R) of 38. What is his Risk-Taking z-score (hint: you will need to find the Risk-Taking mean and standard deviation)?

a. 0.179

b. -0.223

c. 1.342

d. -1.223

**#7. ** Perform independent sample t-tests on the Lifestyle, Dependency, and Risk-Taking scores (L, D, and R) comparing men and women (GENDER1). Use *p* < .05 as your alpha level and apply a two-tailed test. On each of the three scales, do men or women have a significantly higher score?

a. Lifestyle: Men, Dependency: Women, Risk-Taking: Men.

b. Lifestyle: Not significantly different, Dependency: Women, Risk-Taking: Men

c. Lifestyle: Women, Dependency: Women, Risk-Taking: Men

d. Lifestyle: Men, Dependency: Men, Risk-Taking: Not significantly different

**#8.** The median US salary is $50,700, according to US Census data. Using a one-sample t-test, test to see if participant income (INC1) is different from the national average. Use a two-tailed test and an alpha level of 5%.

- Participant income is significantly greater than the national average
- Participant income is significantly less than the national average
- Participant income is not significantly different from the national average
- Participant income cannot be compared to the national average