PSYC 515
HOMEWORK: ANOVA SPSS A SSIGNMENT
Scenario 1
A psychologist at a private mental health facility was asked to determine whether there was a clear difference
in the length of stay for patients with different categories of diagnosis. Looking at the last seven patients in
each of the three major categories, the results (in terms of weeks of stay) were as follows. Using the data
below, test whether the length of stay for patients vary based on category of diagnosis.
Diagnosis Category
Affective Disorders Cognitive Disorders Drug-related Conditions
7 12 8
6 8 10
5 9 12
6 11 10
9 11 9
5 10 11
6 9 12
1. In this specific scenario, what is the independent variable? Is it between or within subjects? How
many levels does it have, and what are they?
ANSWER The independent variable is the diagnoses of the patients.
It is between subjects.
The levels are the three categories: Affective disorders, cognitive disorders, drug-related conditions.
2. Paste all relevant statistical output in the space provided below:
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ANSWER
3. Create an appropriate graph in SPSS and paste it in the space provided below:
ANSWER
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4. Present the results using APA format. This includes a full write-up to include a complete statistical
notation as shown in the weekly presentations. The write-up also needs interpretation. If significant,
state . If it is not significant, what does that mean in layman’s terms? Additional examples of how
APA results sections are also available in the “Helpful Hints” document. (5 pts)
ANSWER
A One-Way Repeated Measures ANOVA was carried out. A comparison was done between the final seven
patients in each of the three main categories, in addition to total weeks of stay. The null hypothesis was
rejected, F (2,12) = 12.956, p = .001, np 2 = .683.The post hoc pairwise comparisons showed that the patients
diagnosed with affective disorder stayed for a much shorter period then patients with the other two disorders.
The highest length of stay was for patients diagnosed with drug-related issues
5. What is a potential confounding variable in this scenario? Explain your rationale.
ANSWER A potential confounfing variable can be the living situation of the patient. This is because their
environment could potentially be a causing factor as to why they have exposure.
Scenario 2
The following data were obtained from a research study examining the effect of sleep deprivation on motor
skills performance. A sample of five participants was tested on a motor-skills task after 24 hours of sleep
deprivation, tested again after 36 hours, and tested once more after 48 hours. The dependent variable is the
number of errors made on the motor-skills task, shown below. Use the data to test whether or not the number
of hours of sleep deprivation has a significant effect on motor skills performance.
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Participant 24 hours 36 hours 48 hours
A 0 1 5
B 0 0 0
C 1 3 5
D 0 1 5
E 4 5 9
6. In this specific scenario, what is the independent variable? Is it between or within subjects? How
many levels does it have, and what are they?
ANSWER
Independent variable: hours of sleep.
It is within subjects design
The three levels of sleep: 24 hr, 36 hr, and 48 hr.
7. Paste all relevant statistical output in the space provided below:
ANSWER
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8. Create an appropriate graph in SPSS and paste it in the space provided below:
ANSWER
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9. Present the results using APA format. This includes a full write-up to include a complete statistical
notation as shown in the weekly presentations. The write-up also needs interpretation. If significant,
state . If it is not significant, what does that mean in layman’s terms? Additional examples of how
APA results sections are also available in the “Helpful Hints” document. (5 pts)
ANSWER
A repeated-measures ANOVA showed that the number of sleeping hours had a major effect on the total
number of errors on motor-skills task of F (2,8) = 13.857, p = .003, p 2 = 0.776 (Greenhouse-Geisser was Ƞ
used because of the violation of Mauchley’s Test of Sphericity). The null hypothesis was rejected. The LSD
post hoc comparisons showed that individuals make significant errors if they do not sleep for 48 hours.
Scenario 3
It has been suggested that pupil size increases during emotional arousal. A researcher would, therefore, like to
see whether the increase in pupil size is a function of the type of arousal (pleasant versus aversive). A random
sample of five participants is selected for the study. Each participant views all three stimuli: neutral, pleasant,
and aversive photographs. The neutral photograph portrays a plain brick building. The pleasant photograph
consists of a young man and woman sharing a large ice cream cone. Finally, the aversive stimulus is a graphic
photograph of an automobile accident. Upon viewing each stimulus, the pupil size is measured (in
millimeters) with sophisticated equipment. The data are as follows. Use it to test whether pupil size varies
based on type of arousal.
Stimulus
Participant Neutral Pleasant Aversive
A 4 8 3
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B 3 6 3
C 2 5 2
D 3 3 6
E 3 8 4
10. In this specific scenario, what is the independent variable? Is it between or within subjects? How
many levels does it have, and what are they?
ANSWER
The independent variable is the stimulus that the participants are exposed to.
This example is within subjects design
There are three levels: Neutral, pleasant, and aversive.
11. Paste all relevant statistical output in the space provided below:
ANSWER
Descriptives
Pupil_Size
N Mean Std. Deviation Std. Error
95% Confidence Interval for Mean
Minimum MaximumLower Bound Upper Bound
Neutral 5 3.0000 .70711 .31623 2.1220 3.8780 2.00
Pleasant 5 6.0000 2.12132 .94868 3.3660 8.6340 3.00
Aversive 5 3.6000 1.51658 .67823 1.7169 5.4831 2.00
Total 15 4.2000 1.97122 .50897 3.1084 5.2916 2.00
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12. Create an appropriate graph in SPSS and paste it in the space provided below:
ANSWER
13. Present the results using APA format. This includes a full write-up to include a complete statistical
notation as shown in the weekly presentations. The write-up also needs interpretation. If significant,
state . If it is not significant, what does that mean in layman’s terms? Additional examples of how
APA results sections are also available in the “Helpful Hints” document. (5 pts)
ANSWER
Based on a repeated measures ANOVA it was found that pleasant stimulus had a major impact on pupil size
of F (2,8) = 13.857, p = .042, p 2 = .548. The null hypothesis was rejected. The post hoc comparisons Ƞ
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showed that the pupil size of participants increased when they were exposed to a pleasant photograph.
Note: Your assignment will be checked for originality via the Turnitin plagiarism tool.
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