For each study design below, choose whether it is a one sample
Sample t, independent t and repeated measures.
1. For each study design below, choose whether it is a one sample T, an independent T, or a
repeated measures T. (1 point each)
a. A classroom of students get a math training module and their scores are measured before and
after.
b. One classroom of students gets a math training module, and a different classroom of students
doesn’t, and their scores are compared.
c. A classroom of students gets one math training module and then takes a math test. Then the
same students get a different training module, and retake the same math test, and the scores
are compared.
d. A classroom of students gets a math training module, and their test scores are compared to
existing national test scores
2. What exactly is MD? How do you get it? How does it relate to the null hypothesis Mew? Actually
understanding what this is, and reminding yourself of it clearly, will help keep you from getting
confused in this chapter (2 points)
3. The following data were obtained from a repeated-measures research study. What is the value
of MD for these data? (1 point)
Subject 1st 2nd
#1 15 #2
#3 5
7 8
5 15 Sample t, independent t and repeated measures.
#4 4 11
-2 or 2
4. Describe the steps for calculating the above M D (1 point)
5. In a repeated measures design, what raw scores do you use to get the standard error?
6. A repeated-measures study using a sample of n = 28 participants would produce a t statistic
with df = ____. (1 point)
7. A researcher uses a repeated-measures study to compare two treatment conditions with a set of
19 scores
in each treatment. What would be the value of df for the repeated-measures t
statistic? Think about this carefully. (hint: be sure you understand what is n in a repeated
measures study, and how you get the df?)
8. A repeated-measures study and an independent-measures study both produced a t statistic with
df = 22.
How many individuals participated in each study? (hint: ITS NOT THE SAME
NUMBER FOR BOTH!) (1 point)
9. Explain your answer to number 7. (1 point)
10. What is the correct null hypothesis for a repeated-measures t test? (1 point) Sample t, independent t and repeated measures.
11. A sample of difference scores has a mean of M D = 5 with a variance of s2 = 144. If effect size is
measured using Cohen’s d, what is the value of d? (1 point)
12. A researcher obtains t(20) = 4.00 and M D = 9 for a repeated-measures study. If the researcher
measures effect size using the percentage of variance accounted for, what value will be
obtained for ?2?
(1 point)
13. A researcher conducts a repeated-measures study to evaluate a treatment with a sample of n =
16
participants and obtains a t statistic of t = 1.94 and a sig (or p) value for
that specific T value of .03. The treatment is expected to increase scores and the sample mean
shows an increase. Accept or reject the null for a one tailed test using ? = .05? (1 point)
14. A research report describing the results from a repeated-measures study states: The data show
no
significant difference between the two treatments, t(10) = 1.65, p > .05. Based on this
report, you can conclude that a total of ____ individuals participated in the research study. (1
point)
15. Compared to an independent-measures design, a repeated-measured study is more likely to find
a
significant effect because it reduces the contribution of variance due to ______. (1 point)
16. A sample of college students is used to test the effectiveness of a new Study Skills Workshop.
Each student’s grade point average (GPA) is recorded for the semester before the
workshop and for the semester after the workshop. The average GPA improved by M D = 0.60.
The 95% confidence interval is .60 plus or minus .15. What does that mean in terms of the
actual numerical improvement in gpa? (1 point) Sample t, independent t and repeated measures.
17. Briefly explain the advantages and disadvantages of using a repeated-measures design as
opposed to an independent-measures design and given an example (2 points). Don’t just say
whatever comes into your head, have a look in your text.
18. A researcher wants to examine how the chemical tryptophan, contained in foods such as turkey,
can affect mental alertness, at an alpha of .05, two tailed.
A sample of n = 9 college students is obtained and each student’s performance on a
familiar video
game is measured before and after eating a traditional Thanksgiving dinner
including roast turkey.
The average decrease in scores was M = 12 points after the meal with variance = 144 for the
difference
scores. Answer the questions below (6 points total this problem). a. What are the df? (1 pt) b. What is the Standard error? (1 point) c. What is the calculated value
of T? (1 point) d. Assume the critical cutoff for a two tailed T is plus or minus 2.306. Is your finding significant
or not? Say something about why you can or cannot reject the null. (1 point) Sample t, independent t and repeated measures. e. Compute ?2 to measure the size of the
effect. (1 point) f. Write a sentence demonstrating how the outcome of the test and the measure of effect
size would appear in a research report. (1 point)
