homework section F

PSYC 317 – Spring 2015: Exam 3

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.

Completion (37 points)

Complete each sentence or statement.

1. For a one-way Analysis of Variance, if the variance between groups is due only to chance we expect our F-test statistic to be equal to ________ (1 point).

2. A 2x4 factorial ANOVA analyzes _____ independent variable(s) (1 point).

3. If repeated administrations of a test to the same individual leads to identical scores on the test, we say that the test is _________________, however if a test accurately measures the intended psychological construct, we say that a test is _________________ (2 points).

4. One needs to use a __________________ test after an ANOVA only if it is significant (1 point).

5. The SS-within will never be _________________ (greater or smaller) than the SS-error (1 point).

6. Main effects test for differences among ______________ means, whereas the interaction tests for leftover differences among the _________________ means (2 points).

7. A correlation between a dichotomous (2 category) variable and a continuous variable is called a _______________________ correlation, whereas a correlation between two continuous variables is called a ___________________ correlation (2 points).

8. In regression, ________________ represents the predicted change in Y when X is increased one point/unit (1 point).

9. For regression, the _________ __________ reflects the typical deviation between a predicted Y and actual Y (1 point).

10. Complete the following ANOVA table for a one-way design with 5 different treatment conditions with n = 12 people in each condition. (8 points)

Source	SS	df	MS	F	p
Between Groups			10
Within Groups
Total	150

11. Complete the following ANOVA table for a factorial design. Dr. Sousa wanted to see if gender and/or dog ownership influences the number of digital songs a person own. He found out how many digital songs each person owned (the DV). He also recorded their gender (either male or female) and whether they owned a dog (yes or no). n = 10 for each condition (17 points)

#Source	SS	df	MS	F	p
Between treatments	24
Gender
Dog Ownership	12			4
Gender x Dog	4
Within			3
Total

Short Answer (19 points)

Choose one of the following two short answer problems.

1. Describe at least two of the commonly used applications/purposes for which researchers use correlations (2 points).

2. Describe briefly two situations when one would use a Spearman correlation instead of a Pearson correlation. (2 points)

Choose one of the following two short answer problems.

3. Describe the two stages for computing a repeated-measures ANOVA by hand. (2 points)

4. Describe at least two advantages to using an ANOVA or Factorial ANOVA to analyze your data rather than multiple t tests (2 points).

For each of the following scenarios, identify the independent variable(s), the dependent variable, and the best inferential test from this course to test the hypothesized relationship. Remember, the correct answer might be any inferential technique discussed over the entire semester. (3 points each)

Dr. Matthews would like to investigate the differences in suicide ideation among individuals of different religions (Catholic, Protestant, Jewish, Islamic). She is also interested in gender differences (males versus females) in suicide ideation. She records suicide ideation in each individual using an interval response scale, as well as their religious affiliation and their gender.

Predictor(s)/IV(s):______________________

Criterion/DV:_______________________

test:________________________

Dr. Peterson wants to see if vegetarianism (yes/no) has an effect on political conservatism. He gives a (continuous) conservatism assessment to a sample of vegetarians and a sample of meat-eaters. He then compares the scores from each sample to see if there is a significant difference in political conservatism between the two groups.

Predictor(s)/IV(s):______________________

Criterion/DV:_______________________

test:________________________

Dr. Kilduff is interested in examining the relationship between depression and binge eating. He gives a sample of eating disorder patients an assessment of their depression levels on a continuous scale and then counted how many calories they eat each day. He compares the assessment scores from each individual to see if there is a relationship between depression and caloric intake.

Predictor(s)/IV(s):______________________

Criterion/DV:_______________________

test:________________________

Dr. Dillamond collected a sample of workers who have flexibility in where they can work, and he assessed their productivity (a continuous variable) in three different places: in their home, in their office, and in a neutral location (i.e., a café with internet access) to determine if there are productivity differences by location. He assesses each participant in all three locations.

Predictor(s)/IV(s):______________________

Criterion/DV:_______________________

test:________________________

Thirty participants watch a 10-minute video clip of a comedy television show. After a 1-hour break, the same participants return to watch a 10-minute video clip of a reality television show. After each showing, participants rate how much they like the shows on a ratio scale.

Predictor(s)/IV(s):______________________

Criterion/DV:_______________________

test:________________________

Problems (82 points)

Remember you MUST show your work to receive full credit.

1) Dr. Martin wants to determine if video game playing is related to how much one values education. She asks people to report how many hours a week they play video games, and then asks them to rate how important education is to them on a 1 (not important) to 10 (very important) scale. She believes that people who play more video games will value education less. Use the data below to answer the following questions:

Hours of game playing	Education rating
6	8
3	5
12	2
10	4
8	6
2	10

What is the alternative hypothesis in words and statistical notation (2 point)?

What is the null hypothesis in words and statistical notation (2 point)?

What is the critical value (1 point)?

Compute the test statistic (8 points):

What do you conclude regarding the null hypothesis test and the research question (2 points)?

Compute an effect size and interpret it (2 points).

2) Professor Miles wants to examine the makeup of her final grades for students. She wants to know if there were any gender differences, differences based on semester, or an interaction between the two effects. The data below reflect average final grade by gender and semester. They are also shown in the associated chart.

	Spring	Summer
Male	M = 75, T = 825 SS = 150, n = 11	M = 65, T = 715 SS = 180, n = 11
Female	M = 73, T =803 SS = 150, n = 11	M = 81, T = 891 SS =200, n = 11

What are the alternative hypotheses (3 point)?

What are the null hypotheses (3 point)?

What are the critical values (1 point)?

Compute the test statistics (16 points):

What do you conclude regarding the null hypothesi ( T = 1540 ) ( T = 1694 ) ( G = 3234 ) ( T = 1628 ) ( T = 1606 )s test and the researcher’s question (3 points)?

3) Dr. Hawkins wants to determine if cologne can actually increase the number of phone numbers a man can get at a bar. He randomly samples 20 male college students and assigns them to one of four conditions: control condition (no cologne), Tag, Axe, and Old Spice. Participants sprayed their cologne 30 minutes before entering the bar. The amount sprayed was identical for each participant. The data below report how many phone numbers each participant obtained.

Control	Tag	Axe	Old Spice
4	3	5	2
6	5	9	1
7	2	10	3
5	4	8	4
7	2	9	1
SS = 6.8	SS = 6.8	SS = 14.8	SS = 6.8

N = 20, G = 97, X2 = 615

What is the alternative hypothesis in words and statistical terms (2 points)?

What is the null hypothesis in words and statistical terms (1 point)?

What is the critical value (1 point)?

Compute the test statistic and report the data in an ANOVA table format (9 points)?

Source	SS	Df	MS	F	p
Between
Within
Total

What do you conclude from these data regarding the research question and the hypothesis test (2 points)?

Compute and interpret an effect size measure (2 points).

4) Dr. Pappas is investigating whether diet influences people’s intelligence scores. He gathered a sample of 33 participants and assessed their IQ. He also collected information on whether they were vegan, vegetarian, or omnivores. The data he collected is displayed below. He calculated a one-way ANOVA and found that there is a significant difference somewhere. However, post hoc analyses need to be conducted to assess where those differences lie. The source table is also displayed below.

Vegans	Vegetarians	Omnivores
M = 95 T = 1045 n = 11	M = 100 T = 1100 n = 11	M = 110 T = 1210 n = 11

Source	SS	df	MS	F	p
Between	1283.33	2	641.67	8.00	< .05
Within	2406.25	30	80.21
Total	3689.58	32

Compute and interpret a post-hoc measure of your choice. What do you conclude (i.e. is each difference significant)? (4 points)

5) A researcher collects information from a group of participants about many miles per hour they usually drive above the speed limit (a continuous variable), and how many traffic incidents they’ve been involved in throughout their life (e.g., receiving tickets or being in collisions, also a continuous variable). The researcher decided to run a Pearson correlation analysis on the data, and finds that SP = 2 for the two variables. Additionally, for mph above the speed limit, he finds M = 10, and SS = 4. For number of traffic incidents, he finds M = 6, and SS = 5. However, he changes his mind about the analysis, and decides to perform a regression so that he can predict number of traffic incidents based on amount speeding.

Calculate b for the data (with speeding predicting number of incidents) (2 points).

Interpret b (2 points).

Calculate a for the data (2 points).

Interpret a (2 points).

6) Dr. Inman believes that environment influences physical abilities. He conducts a repeated-measures design to assess if environment influences how fast someone runs 5 miles. He gathers 5 participants, and has them run 5 miles each at the gym on a treadmill, outside in a residential neighborhood, and outside on a running trail in a park. All participants run in each of the conditions, though there is adequate rest between trials (2 days), plus the order of trials is randomized for each participant. His recorded data are below (time in minutes):

	Gym	Neighborhood	Park	P
A	46	56	51	153
B	68	78	79	225
C	49	51	49	149
D	36	46	51	133
E	58	65	59	182

Dr. Inman goofed up and accidentally ran his data as a one-way between-subjects ANOVA! His results were not significant:

Source	SS	df	MS	F	p
Between-groups	172.9333	2	86.4667	0.5606	.585
Within-groups	1850.8000	12	154.2333
	2023.7333	14

Fix his results for him. Correct his mistake, and calculate what his results should be for the correct method, a repeated-measures ANOVA. Be sure to do these calculations by hand, and show your work.

HINT: He already did half of your work for you by running his ANOVA.

Compute the test statistic (6 points):

What do you conclude from these data regarding the research question and the hypothesis test (2 points)?

Calculate and interpret a measure of effect size (2 points).

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