Behavioral Statistics
| Homework #4 - Two-Sample t-tests (Independent Measures & Dependent Measures Designs) |
For each problem, Download the data from the Problem Description (see below). Calculate all appropriate descriptive statistics and test the hypothesis with an appropriate alpha (α) level. Don't forget an APA-style write up of your results. APA-style examples are located here.
| Problem Description 1 |
Your job here is to evaluate the effect of a drug on
learning a complex problem-solving task. The drug group (7 monkeys)
received pills, while the other group (6 monkeys) was given an inert substance
(i.e., a placebo). Pills and training on the task continued for 6 days.
The total number of errors for each monkey was the dependent variable.
Using a t-test, analyze these data and draw conclusion.
| Problem Description 2 |
Imagine being lost at sea, bobbing around in an orange life jacket. The Coast Guard sends out two kinds of observers to spot you, fellow humans and pigeons. All observers are successful; the search time for each is given in the data file in minutes. Using an alpha-level of 1% (p <.01), analyze the data and write a conclusion.
| Problem Description 3 |
| The data in this dataset
were the Trials Through Criterion (ttc) for 10 successful reversals in the Greek
Cross water maze. Saline- and Ecstasy-treated rats were compared.
On the basis of the evidence, what is your conclusion.
|
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| Problem Description 4 |
The NEO PI-R, the standard questionnaire measure
of the Five Factor Model (FFM), provides a systematic assessment of emotional,
interpersonal, experiential, attitudinal, and motivational styles-a detailed
personality description that can be a valuable resource for a variety of
professionals. The NEO PI-R is a concise measure of the five major domains of
personality, as well as the six traits or facets that define each domain. Taken
together, the five domain scales and 30 facet scales of the NEO PI-R, including
the scales for the Agreeableness and the Conscientiousness domains, facilitate a
comprehensive and detailed assessment of normal adult personality. It has useful
applications in counseling, clinical psychology, psychiatry, behavioral medicine
and health psychology, vocational counseling and industrial/organizational
psychology, and educational and personality research.
Each of these global factors consist of more specific personality traits. What
follows are the names of the factors and the more specific traits of people
scoring high vs. low on the factor:
| I. NEUROTICISM: Hi: Anxiety, Angry Hostility, Depression, Self-consciousness, Impulsiveness, Vulnerability. Lo: Calm, Even-tempered, Relaxed, Composed, Confident. II. EXTRAVERSION: Hi: Warmth, Gregariousness, Assertiveness, Activity, Excitement Seeking, Positive Emotions (upbeat, energetic). Lo: Reserved, Independent, Even-paced, Less exuberant, Serious. III. OPENNESS TO EXPERIENCE: Hi: Active imagination, Artistic, Attention to inner feelings, Preference for variety, Intellectual curiosity. Lo: Narrower scope of interests, Conventional in thought, Conservative, Cautious in thought. IV: AGREEABLENESS: Hi: Trust, Straightforwardness, Altruism, Compliance, Modesty, Tender-mindedness, Cooperative. Lo: Skeptical, Ego-centric, Competitive, Headstrong.
V: CONSCIENTIOUSNESS: |
The data here are for comparison between CIS majors and
Marketing majors. Also included is a Service Orientation score, a
Religiosity score, and GPA. Using t-tests, analyze these data and draw
conclusions.
| Problem Description 5 |
The dataset here is also from the NEO-R and associated
scores. Using t-tests, compare males versus females on each variable and
draw conclusions.
| Problem Description 6 |
Suppose you are interested in studying the effects of
interracial contact on racial attitudes. You have a fairly reliable test
of racial attitudes in which high scores indicate more positive attitudes.
You administer the test one Monday morning to a group of 14-year-old girls of
different racial backgrounds. They don't know one another beforehand but
all have signed up for a 1-week day camp. The campers then spend the next
week taking nature walks, playing ball, eating lunch, swimming, making things,
and doing the kind of things that camp directors dream up to keep 12-year-olds
busy. On Saturday the girls are again given the racial attitudes test.
What do these data suggest?
| Problem Description 7 |
A researcher studies the effects of a drug (an SSRI) on
the number of nightmares occurring in Iraqi Conflict veterans with post
traumatic stress disorder (PTSD). A sample of PTSD clients records each
incident of a nightmare for 1 month before treatment. Subjects are then
given the drug for 1 month, and then they continue to report each occurrence of
a nightmare. Can we conclude that the SSRI reduces nightmare frequency?
| Problem Description 8 |
Run these data two ways.
INDEPENDENT SAMPLES
Sample 1: 199 261 295 183 161 104 199 248 105 197 249 218
Sample 2: 286 211 121 134 210 68 166 157 258 184 116 203
MATCHED PAIRS
Pair:
1 2
3 4
5 6
Sample 1: 218
144 286 208
234 256
Sample 2: 154
160 239 198
211 241
Pair:
7 8
9 10 11
12
Sample 1: 133
87 224 212
256 133
Sample 2: 136
39 192 183
215 117
Datafile =
Using the data taken from independent samples, test to determine whether the means of the two populations differ (Use α = .05).
Using the data taken from dependent samples (matched pairs; aka, a dependent-samples t-test), test to determine whether the means of the two populations differ (Use α = .05).
Why are they different?
© 2008, David M. Compton, Ph.D.
