PSYC 510
Part I: General Concepts
These questions are based on the concepts covered in this
module’s assigned readings and presentations.
Answer the following questions using your own words.
1. Explain what counterbalancing is, how it is achieved, and which confound it helps to minimize.
ANSWER
Counterbalance is a technique used to to control order effects. It is achieved by mixing up the orders for
the interventions the participants will receive. Counterblance helps minimize errors related to order
effects.
2. Using your own words, discuss how a correlated-groups test has more statistical power in t
comparison to an independent-groups test.t
ANSWER
A correlategroups t test has more statistical power in comparison to an independent-groups t test as it
compares two groups of participants. In addition to this each group is tested twice.
3. Discuss one strength and one weakness of a within-subjects design using your own words.
(Do not include statistical power, as it is assessed in a previous question)
ANSWER
One strength of a within-subjects design is it requires fewer participants. One weakness of a
withinsubject is testing effect. Since participants are tested multiple times practice and fatigue effect can
be a problem.
SCENARIO: A researcher believes exercise may affect anxiety in women, but research appears
inconclusive. She identifies a group of women (N = 30) who had not exercised before, but are now
planning to begin exercising. She gives them a 50-item anxiety inventory before they begin exercising and
administers it again after 6 months of exercising. The anxiety inventory is measured on an interval scale
and higher numbers indicate higher anxiety. In addition, scores on the inventory are normally
distributed. The mean of the difference scores is 3.4, S = 1.8, and there were 30 in the sample. Using this
D
information, answer the following questions showing all work when calculations are required to earn up
to full credit.
4) Calculate the correlated-groups test to determine the . (Note you will first have to solve for the standard t tobt
error of the difference score).
Work: Standard error: 1.8/√(30)=1.8/5.4772=0.3286 For T: T=(3.4-
0)/0.3286=3.4/0.3286=10.3469 ANSWER obtained: t 10.3469
5) Calculate the effect size using Cohen’s d. Interpret it using the appropriate conventions (small, medium, or
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PSYC 510
large).
Work: d=3.4/1.8=1.89 ANSWER d=1.89 large effect size
6) Is this a directional or non-directional study, and what is the ? (Note you will have to first calculate t cv
the df)
Work: df= 30-1 = 29 ANSWER Non directional t = 2.045
cv
7) Calculate the 95% confidence intervals (make sure you use the two-tailed ).t cv
Work: 3.4 + 2.045(.3286)= 4.07 AND 3.4 – 2.045(.3286)= 2.73 ANSWER 4.07, 2.73
8) Write an APA-style Results section based on your analyses. All homework “Results sections” should
follow the examples provided in the videos. Don’t forget to include the effect size, confidence interval, and
a decision about the null hypothesis.
ANSWER
A correlated groups t test examined whether erxercies effects anxiety in women. It was statistically significant t
(29)= 10.35, p<.05 two tailed, d= 1.89, 95% CI [4.07, 2.73]. The null hypothesis is reected and it is concluded
that exercise does affect anxiety in women.
Part II: SPSS Application
These questions require the use of SPSS. Remember you must
submit all of your work within this word document. You will need
to take a screen shot of your data view if necessary, or copy and
paste your output into the spaces below. Remember to report the
exact p value provided by SPSS output – simply reporting p<.05 or
p>.05 is not acceptable (unless SPSS output states p=.000 – in that
case you can report p<.001).
Research Scenario: Do you cope better than peers when facing difficult situations? In one
study, researchers reported that most individuals believe that they can cope better than their
fellow students (Igou, 2008). A recent researcher wanted to replicate the study. In this design,
participants read a scenario of a negative event and were asked to use a 10 point scale to rate
how it would affect their immediate well being (1 – 10, the higher the score, the better the
mood). They they were asked to imagine the event from the perspective of an ordinary fellow
student and rate how it would affect that person using the same scale.
Using the information provided, create an SPSS data file and conduct the appropriate
statistical test to determine whether people believe they can cope than their peers. better
Answer the following questions based on your analyses.
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PSYC 510
9) Conduct a correlated groups t-test. Paste the appropriate SPSS output below.
ANSWER
10) Use the output to calculate r (show your work in the space provided and remember if
2
a number is negative, when squaring it will lose its sign and be positive). Interpret it
(small, medium, large) based on the conventions for this effect size calculation.
Work: 4.18 /( 4.18 +11¿ = 17.47/28.47=.61 r =.61 Medium effect
2 2 ANSWER: 2
11) Paste an appropriate SPSS graph (make sure you use the procedures outlined in this
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Self-rating Rating of peer
4 4
8 6
7 6
5 5
7 6
5 4
3 2
5 4
2 2
7 7
8 7
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PSYC 510
module’s SPSS video– and don’t forget to label your y axis “Coping Ability”.
ANSWER
12) Write an APA-style Results section based on your analyses. All homework “Results
sections” should follow the examples provided in the videos. Don’t forget to include the
effect size, confidence interval, and a decision about the null hypothesis. If significant,
make sure you interpret how the conditions differ (refer to the Figure or report the
means and standard deviations).
ANSWER
A correlated groups t test examined if subjects cope better than their peers when facing
difficult situations. It was statistically significant t ( 11) = 4.18, p< .05, one tailed, r2 = . 61,
95% CI [.36, 1.14]. The null hypothesis is rejected. Subjects identify as coping better than
their peers when faced with difficult situaions as shown in figure 1
Part III: Cumulative
These questions can be related to anything covered thus far in the
course.
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PSYC 510
Does amount of information retained differ when participating in meetings in-person verses
virtually? In this study, participants got to choose whether they attend a quarterly meeting
in person or via Google Meet. After the meeting, they were given a brief assessment of
information covered – percent correct for each condition is presented in the table below.
Using the information provided, create an SPSS data file and conduct the appropriate
statistical test to determine whether there is a statistically significant in amount difference
of information retained based on whether attendance is in-person or virtual. Answer the
following questions based on your analysis.
13) Clearly identify the independent and dependent variables in this scenario.
ANSWER
The independent variable is how the meeting is being held ( either virtually or in person).
The dependent variable is the amount of knowledge the participant retains.
14) Paste the output of your statistical analysis below.
ANSWER
15) Create an appropriate graph based on the data and paste it below (make sure
to have axes labels and error bars).
ANSWER
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In-Person Virtual
78 67
65 80
79 72
84 69
91 92
88 75
79 79
89 66
90 71
85 69
PSYC 510
16)
Write an APA-style Results section based on your analyses. Remember to use
complete sentences, include the statistical notation, effect size, confidence
interval, and include a decision about the null hypothesis. If it is significant,
state how by reporting the means and standard deviations or refer the reader
to the previous Figure.
ANSWER
An independent samples t test examined the difference in the amount of information
retained in a meeting depending on it it was virtual or in person. The independent samples t
test showed that it was statistically significant t (18) = -2.49, p<.05, two-tail r =.27, 95% CI
2
[16.22, 1.38]. The null hypothesis is rejected. Participants who were in the in-person
meeting retained more information than the participants in the virtual meeting.
17) Discuss one threat to internal validity as it specifically relates to this research
scenario.
ANSWER
One threat to external validity is sampling bias as the particpaints were given the option to
choose if they wanted to attend in person or virtually. What if those that choose virtually
picked because they knew they would have the fexiabilty to do other things instead of
paying attention.
Use this information to answer the following questions:
Age at onset of dementia was determined in the general population to be = 70 and
= 7.0.
18) Based on the data above, what is the z score for someone being diagnosed with
dementia at age 65 (can round to two decimal places)? What percentage of
people might start to show signs of dementia before this age ( DO NOT
ROUND).
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PSYC 510
z score = -.71
ANSWER
% = 23.884
ANSWER
Work: z= (65-70)/7= -5/7= -.71
Done!
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