SRM 2 Statistics and Research Methods Homework

Fall '05

Note: These due dates are subject to change. If there is a conflict between what you see here and what the instructor says in class, go with what is given in class.
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Homework Assignment #1

The first homework assignment will be given out in class and will be based on your performance on the pretest.† If you get all the answers right on the pretest, you won't have to turn anything in, and will get 10 pts.† For everyone else, the problems you need to do will be indicated on the assignment handed out in class.

10 pts.

Due:† Sept. 8, 2005
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Homework Assignment #2

This assignment should be turned in in the form of printed output from SPSS. You can use SPSS in S 208 or the second floor of the classroom building. You do not need to turn in the data set.

1. Calculate the following:

††† a. the mean, standard deviation, and variance for number of hours spent studying

††† b. the mean, standard deviation, and variance for number of hours spent watching TV

2. Print out a frequency histogram for hours spent studying, and a separate histogram for hours spent watching TV.

3. Print out the correlation between hours studying and hours watching TV.

4. Print out a plot of hours studying, as a function of hours watching TV.

10 pts

Due: Sept. 13

Homework Assignment #3

† Hieman, p. 395, #14,

††† (note that question d is asking whether or not to reject the null hypothesis)
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5 pts

Due:† Sept. 20
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Homework Assignment #4

In the general population, 10% of all households access the internet using DSL, 40% use a modem, and 50% do not have internet access.† In order to determine whether NEIU students differ from the rest of the population, Dr. Smith randomly selects 350 students and asks them whether and how they access the internet from home.† Out of the 350, 30 report using DSL, 150 use a modem, and 170 do not have internet access from home.† Answer the following questions.
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A.† What are the null and alternative hypotheses?
B.† What are the expected values for each of the 3 types of internet access categories?
C.† What is chi-square obtained?
D.† What is the critical value?
E.† Should the null hypothesis be rejected?† Why, or why not?

5 pts

Due: Sept. 22

Homework Assignment #5

This assignment is based on an article by Martin Orne and Frederick Evans, entitled "Social Control in the Psychological Experiment: Antisocial Behavior and Hypnosis"; you may also want to read the original research article by Loyd Rowland (1939), entitled "Will Hypnotized Persons Try to Harm Themselves or Others?"

Note:† This assigmnent must be typed, double-spaced.

1. List some of the problems with the original study by Rowland with regard to internal validity. In other words, did he control for possible confounding variables? Were the control and experimental (hypnotized) group treated exactly the same except for the treatment? etc.

2. List some of the problems with the Rowland study with regard to external validity. In other words, can his results from the lab be generalized to the rest of the world?

3. What did Orne and Evans do to control for some of these problems?

4. Rowland had concluded that hypnotized subjects would perform dangerous acts that nonhypnotized subjects would not perform. How would you reinterpret his results, based on the Orne and Evans study?

10 pts

Due: Oct. 11

Homework Assignment #6

The Pepsi Challenge

This homework assignment will be to write the Method, Results, and Discussion sections of an experiment carried out in class (the Pepsi Challenge, described below). All papers must be typed, using APA format (double-spaced, 10 or 12-pt font, 1" margins).

The Pepsi Challenge will be conducted to determine whether people prefer the taste of one cola over the other. Specifically, subjects will be asked which they prefer before tasting the two colas. They will then taste and rate them in a blind taste test. We will design and carry out the study together as a class on Feb. 15. We will also do the analyses in class, but you will be responsible for reporting and making sense out of them.

20 pts.

Due: Oct. 13

Homework Assignment #7

Heiman p. 426 #16

††† note that the last question is asking for the effect size

5 pts

Due:† Oct. 18

Homework Assignment #8

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Heiman p. 452 #24; the last question is asking for the effect size

5 pts

Due:† Oct. 25

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Homework Assignment #9

Calculate a 1-way between-subjects ANOVA for the following two experiments. For the first, you have been given the sum of squares so you can check and make sure you're doing it right, however you must still show your work (calculations for SS) to get full credit. Please put all of your work and answers on a separate page.

1. Subjects were randomly assigned to one of three conditions: earned money, surprise money, or gift money. In the earned money condition, the subjects read a scenario that described them earning $50. In the surprise condition they read a scenario in which they voluntarily did some work and were later surprised by being paid $50 for the work. In the gift money condition, they read a scenario in which they won $50 in a raffle. After reading the appropriate scenario, each subject indicated how much of the $50 he or she would save. The data are below:

Earned†††††† Surprise††††††††† Gift
50††††††††††††† 40††††††††††††† 40
30††††††††††††† 50††††††††††††† 20
40††††††††††††† 40††††††††††††† 25
45††††††††††††† 30††††††††††††† 30
45††††††††††††† 45††††††††††††† 35

a. What are the null and alternative hypotheses?

b. Calculate an ANOVA and fill in the following summary table:

††††††† Source††††††††† df††††††††††††† SS††††††††††††† MS††††††††††††† F†††††††††††††† Fcv

Between groups††††††††††††††††††††††††† 443.33
Within groups†††††††††††††††††††††††††† 700
Total††††††††††††††††††††††††††††††††† 1143.33

c. Should the null hypothesis be rejected?
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2. Twelve rats are trained to press a bar on one of three schedules of reinforcement: a continuous reinforcement schedule, a fixed interval schedule (reinforced every 2 minutes as long as at least one response has occurred), and a fixed ratio schedule (reinforced every 4 responses). The number of responses that occurs during a 10-minute test period is recorded, and a response per minute score is calculated for each rat. The data are below:

Continuous††††† Fixed Interval††††††††† Fixed Ratio
††††††† 3.5†††††††††††† 1.3†††††††††††††††††††† .60
††††††† 4.0††††††††††††† .90††††††††††††††††††† .30
††††††† 3.8†††††††††††† 1.5†††††††††††††††††††† .70
††††††† 4.2†††††††††††† 2.0†††††††††††††††††††† .50

a. Calculate an ANOVA, and fill in a table like the one presented in problem 1b.

b. Is the null hypothesis rejected?

c. Conduct a Tukey's HSD post-hoc analysis and show which means differ significantly from each other.

d.† What is the effect size?

10 pts

Due: Nov. 10

Homework Assignment #10

This homework assignment is based on a videotape that we will view in class on Feb. 17. If you miss class that day you will not be able to do it.† It is from a Frontline program on Facilitated Communication.

This assignment must be typed, double-spaced.
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1. Briefly describe the experiment that was set up to determine whether facilitated communication was valid. How did they control for possible confounding variables?

2. Why do you think many people, including scientists, continue to believe in facilitated communication despite the lack of evidence for its validity?

5 pts.

due:† Nov. 22

Homework Assignment #11

Professor Smith wants to test the effects of exercise on learning. She uses the students in her two classes as subjects. She randomly assigns half
of the 20 students in her morning class, and half of the 20 students in her afternoon class, to attend an aerobics class every day, just before class.
The dependent variable is the score each student gets on the final exam (out of 50). The independent variables are class (morning or afternoon),
and the treatment (exercise or no exercise). The scores for each subject are listed on the next page.

Your assignment is to enter the data into SPSS and analyze it using a factorial ANOVA. You must turn in:

1. A printout of the output from the ANOVA.

2. A printout of a graph of the results.

3. An APA-style write-up of the results.† This must include a description of all significant effects (i.e. APA style stats, as well as a verbal
description of all effects.

4. Answer the question: Do the results of this study support the idea that exercise helps learning? Why, or why not?
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Scores for non-exercisers in the morning class:† 49† 43† 45† 47† 48† 50† 42† 41† 45† 45

Scores for exercisers in the morning class:†† 48† 38† 43† 38† 40† 42† 44† 38† 38† 43

Scores for non-exercisers in the afternoon class:† 37† 41† 45† 42† 39† 40† 35† 41† 40† 38

Scores for exercisers in the afternoon class:† 48† 46† 47† 48† 45† 47† 42† 43† 45† 50
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10pts

Due: Dec. 6

Homework Assignment #12

This is based on an article titled "Increasing designated driving with a system of prompts and incentives".† Your answers must be typed, double-spaced.

1. How were subjects selected for this study?

2. Briefly describe the "treatment", or independent variable.

3. Briefly describe the "ABAB reversal" design. Why do you think this design was chosen?

4. Why would this be considered quasi-experimental, instead of a true experiment?

5. What are some potential problems you can identify with this study?

5 pts

Due: Dec. 8
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