Liberty University Two Paired Samples Statistics Worksheet
PSYC 510HOMEWORK: TWO-PAIRED SAMPLES T -TESTS ASSIGNMENT INSTRUCTIONS
This Homework: Two-Paired Samples T-Tests Assignment is designed to assess your
understanding of the concepts and applications covered thus far in this course. Concepts specific
to this module include the assumptions for a correlated groups t test, how to calculate it both by
hand and using SPSS, and how to present it using professional conventions. Its strengths and
weaknesses as compared to the independent samples t test from our previous module is also
discussed. Development of knowledge and skills for appropriate use of this popular test, as
required in this Homework: Two-Paired Samples T-Tests Assignment, will prepare you to be
a more informed consumer and producer of research both professionally and non-professionally.
Be sure you have reviewed this module’s Learn section before completing this Homework:
Two-Paired Samples T-Tests Assignment. This Homework: Two-Paired Samples T-Tests
Assignment is worth 60 points. Each question is worth 3 points. Six points are awarded for
Part I contains general concepts from this module’s Learn section.
Part II requires use of SPSS. You will have to take screen shots and/or copy and paste from
your SPSS to place answers within this file. Make sure you only insert relevant and legible
Part III is the cumulative section. These may include short answer and/or use of SPSS but
will review material from previous module(s).
Directions for each subsection are provided in the top of each table (in the blue shaded
Answers should be placed where indicated (wherever there is “ANSWER”).
Submit the file as a WORD document (.doc or .docx). Make sure the filename of your
submission includes your full name, course and section.
o Example: HW8_JohnDoe_510B01
Make sure to check the Homework Grading Rubric before you begin this Homework: TwoPaired Samples T-Tests Assignment.
Part I: General Concepts
These questions are based on the concepts covered in this module’s assigned readings
Answer the following questions using your own words.
Explain what counterbalancing is, how it is achieved, and which confound it helps to minimize.
Page 1 of 6
Using your own words, discuss how a correlated-groups t test has more statistical power in
comparison to an independent-groups t test.
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)
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, SD = 1.8, and there were 30 in the sample. Using
this information, answer the following questions showing all work when calculations are
required to earn up to full credit.
4) Calculate the correlated-groups t test to determine the tobt. (Note you will first have to solve
for the standard error of the difference score).
ANSWER t obtained:
5) Calculate the effect size using Cohen’s d. Interpret it using the appropriate conventions
(small, medium, or large).
6) Is this a directional or non-directional study, and what is the t cv? (Note you will have
to first calculate the df)
7) Calculate the 95% confidence intervals (make sure you use the two-tailed t cv ).
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.
Page 2 of 6
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 is not acceptable
(unless SPSS output states p=.000 – in that case you can report p
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