Part 2

Answer the questions below to the best of your ability. Partial credit will be awarded where possible. You MUST SHOW YOUR WORK for full credit for calculation problems.

Short Answer (17 points)

Dr. Franzen wants to examine a new form of therapy he’s been reading about. The therapy is designed to help those who experience severe anxiety. To assess how well this new therapy works, he collects a sample of 20 participants who had extreme anxiety at the start of the study. He randomly assigns participants to receive either the new therapy or traditional anxiety therapy. After one month, he assesses the level of anxiety for each participant using a survey with a scale from 0 to 7, where 0 represents having no anxiety whatsoever and 7 represents having extreme anxiety. Assume equal distances between consecutive numbers.

1. What type of design is this (1 point)?

2. What is the independent variable / predictor (1 point)?

3. What is the dependent variable / criterion (1 point)?

4. On what scale of measurement is the dependent variable / criterion measured (1 point)?

Dr. Bristow believes that where a student lives influences how much alcohol they consume such that students who live closer to campus will drink more and those who live farther away will drink less. She gives a survey to students asking them how far from campus they live (in miles) and how much alcohol they consume each week (in number of drinks).

5. What type of design is this (1 point)?

6. What is the independent variable / predictor (1 point)?

7. What is the dependent variable / criterion (1 point)?

8. On what scale of measurement is the dependent variable / criterion measured (1 point)?

9. What does it mean if a set of scores has a s = 0? (1 point)

10. What does your data distribution look like if mean < median < mode? Please describe it in words (though you may also draw a picture if you wish). (1 point)

11. Suppose M = 8 and s = 12. If I subtracted 3 from every score in my sample, what would happen to the sample mean and standard deviation? (2 points)

12. Statistics have two general purposes. Describe both ways that we use statistics. (3 points)

13. If someone has a Z-score of -2, what can you conclude? (1 point)

14. What transformation allows researchers to compare two measurements of the same construct with different operational definitions (i.e., different metrics)? (1 point)

Problems (41 points)

Remember you MUST show your work to receive full credit.

X	f
0	1
1	1
2	1
3	3
4	3
5	5
6	5
7	3

1. Using the above data, find the mean, median, and mode (3 points):

Mean = Median = Mode =

Are the data skewed? If so, in which direction are they skewed? (2 points):

2. Standardize the following set of scores (use σ, not s; 5 points): 5, 8, 9, 11, 12

3. Using the concept of real limits, compute the range of the following data (1 point): 2, 8, 6, 5, 10, 14, 7, 9, 13

4. The following set of scores has a mean of 10. Find SS, s2, and σ2. (6 points)

Scores: 6, 9, 10, 10, 15

SS =

s2 =

σ2 =

5. Create the appropriate frequency distribution graph for the following set of continuous scores (4 points):

7, 8, 6, 5, 10, 11, 7, 9, 11

The SAT has a mean of 500 and a standard deviation of 110. Let us assume that the distribution of SAT scores is approximately normal.

6. What is the probability of getting an SAT score between 445 and 580 (4 points)?

7. What is the probability of getting an SAT score less than 620 (2 points)?

8. What raw SAT scores (not Z) separate the middle 80% of scores from the extreme 20% (4 points)?

Mike and his brother Adnan are trying to decide who should do the chores this week. They use a deck of cards to decide, by flipping over one card from the deck at a time (and not replacing them back into the deck).

9. Adnan selects that if the first card drawn is a heart, he will wash the dishes. If it is any other suit, Mike will wash the dishes. What is the probability that Adnan will have to wash the dishes this week (2 points)?

10. After the first card is drawn (a 7 of hearts), Mike selects that if the next card selected is a spade, he will mow the lawn. Otherwise, Adnan will have to mow the lawn. What is the probability Mike will have to mow the lawn this week (2 points)?

11. The second card was a 3 of clubs. So Adnan is now washing the dishes and mowing the lawn this week. Upset about his poor luck, he cheats and sneaks a look at the next card, which is a 6 of spades. He then says that if the next card selected is a diamond, he will vacuum the house. If it is any other number, Mike will have to vacuum the house. What is the probability Adnan will have to vacuum the house this week (1 point)?

Enter the following scores into SPSS. Name this variable Attitude, and label it Attitude Toward Statistics.

15, 12, 8, 9, 8, 10, 11, 13, 11, 6, 12, 10, 7, 9, 11, 10, 12, 11, 9, 14, 13

These scores represent the values from students who were asked how much they like statistics. Each student answered 6 questions, and could rate each question anywhere between 1 (hate that part of statistics) and 3 (love that part of statistics) for each question. Their ratings were summed across all 6 questions to create their total score.

12. Use SPSS to calculate the mean and median for this variable. Right-click to copy the associated descriptive table from your SPSS output, and paste it into Word here (2 points):

13. Write a statement that presents one of the averages for Attitude Toward Statistics, similar to those shown in Chapter 6 of your Holcomb book. Select which average to report based on how skewed the data are. (3 points)