stats help

DESCRIPTIVE STATISTICS PROBLEM SET

1. A distribution has the following properties:

Mean = 60

SD = 8

What is the probability of scoring between 52 and 68?

A. 17%

B. 68%

C. 5%

D. None of the above – provide probability:

2. A distribution has the following properties:

Mean = 0

SD = 20

What is the probability of a score falling between 0 and 40?

A. 48%

B. 68%

C. 95%

D. None of the above – provide probability:

One Sample Test Exercises and Rubric

For each problem below:

1) Determine the appropriate test to perform

2) Compute the test by hand

3) Confirm your computations with Minitab or an online calculator

4) Apply the results to draw a conclusion

5) Write up the conclusion according to APA format

1. Are serial killers more introverted than the general population? A sample of 14 serial killers serving life sentences was tested and found to have a mean introversion score of 42 with s = 6.8. If the population mean is 36, are the serial killers significantly more introverted at the .05 level? Perform the appropriate one-tailed test.

2. A psychologist studying the dynamics of marriage wanted to know how many hours per week the average American couple spends discussing marital problems. The sample mean of 155 randomly selected couples turned out to be 2.6 hours, with s = 1.8.

a. Find the 95 percent confidence interval for the mean of the population.

b. A European study had already estimated the population mean to be 3 hours per week for European couples. Are the American couples significantly different from the European couples at the .05 level? How does your answer to part A make it easy to answer Part B?

Two Sample T-Test Exercises and Rubric

For each question, provide Minitab output for the selected test and write up the results in APA format as you would for a journal article where specified.

1. A group of 30 participants is divided in half based on their self-rating of the vividness of their visual imagery. Each participant is tested on how many colors of objects they can correctly recall from a briefly seen display. The results of this experiment are below:

Vivid	Less Vivid
18	14
17	12
16	13
15	10
14	8
13	8
9	7
8	6
7	5
6	4
5	3
11	2
13	5
18	11
18	14

a. Enter the data into Minitab and perform a two-group t-test of the null hypothesis that vividness of visual imagery does not affect the recall of colors; use alpha = .01, two-tailed. Hint: .01 is not the default alpha level. What is your statistical conclusion?

Result write-up:

b. What are some of the limitations that prevent you from concluding that the visual imagery causes improved color recall in this type of experiment?

2. An educator has invented a new way to teach geometry to high school students. To test this new teaching method, 16 10th-graders are matched into 8 pairs based on their grades in previous math courses. Then the students in each pair are randomly assigned to either the new method or the traditional method. At the end of a full semester of geometry training, all students take same standard high school geometry test. The scores for each student in this hypothetical experiment are as follows:

Traditional	New
65	67
73	79
70	83
85	80
93	99
88	95
72	80
69	100

c. Perform a matched t-test for this experiment (p=.01, two-tailed). Is there a significant difference between the two teaching methods?

Results write-up:

d. Find the 99% confidence interval for the population difference of the two teaching methods. Explain how these confidence intervals confirm the results of the t-test conducted in Minitab.