Unit 6 Assignment: Running and Interpreting a t-Test Using Excel
Due Date:
Points: 100
Overview:
For this assignment, you will apply your knowledge of experimental research to
determine if there is a statistically significant difference between mean (average)
outcomes for an experimental (Intervention group) group and a control group. You will
run “descriptive statistics” and a “t-test” using a sample data scenario and set described
below. The descriptive statistics will tell you means and standard deviations regarding
the outcomes measured; the t-test will tell you if there is a statistically significant
difference between the two means of the outcomes measured.
Instructions:
In a hypothetical study, a researcher randomly assigned participants who had trouble
dieting into one of two groups – an experimental (Intervention group) or a control group.
In the experimental group, participants completed an intervention where were asked to
think about how life would be better if they dieted and how life would be worse if they
did not. Participants in the control group did not receive any sort of intervention. At the
start of the study, all participants weighed 300 pounds. A month after the study began,
participants were weighed again, and the number of pounds lost was recorded. The
data collected is listed below. It was hypothesized that participants in the intervention
group would lose more weight, on average, than participants in the control group.
Intervention Group
(Weight Lost in Pounds)
Control Group
(Weight Lost in Pounds)
20 2
21 1
17 0
18 2
21 0
22 0
16 3
17 1
20 0
16 2
14 4
17 1
22 0
16 3
17 2
PSY341–Research Methods in theSocial Sciences
Part A
For the data set above, determine the following:
1. The mean and standard deviation for weight lost in pounds for the intervention
group. (20 points).
2. The mean and standard deviation for weight lost in pounds for the control group.
(20 points).
Directions for Running Descriptive Statistics in Excel (Means and Standard
Deviations):
In the Resources section of the Unit, review the PowerPoint: “Running a t-Test in
Excel”. This describes how to run both Descriptive Statistics and a t-test.
• Enter the Data Set Above into Excel
• Click Data
• Click Data Analysis
• Click Descriptive Statistics
• Input Range (Select Data Columns)
• Check Summary Statistics
• Click OK
Part B
3. Run a t-test and determine the t statistic. (20 points).
4. Was there a statistically significant difference in mean scores for weight lost in
pounds between the intervention group and the control group? How can you tell?
Look at the p value for assistance. Explain your answer. (20 points).
Directions for Running a t-Test in Excel
• Click DataClick Data Analysis
• Click t-test (assuming equal variance)
• Indicate Variable 1 Range
• Indicate Variable 2 Range
• Enter .05 as your alpha level
• Click OK
Part C
5. Create a bar graph of the means for weight lost in pounds for both the
intervention group and the control group. Add a title and label your axes. (20
points).
Directions for Creating a Bar Graph in Excel
Refer to the video under Readings and Resources in Unit 6, entitled, “Column Graphs
and t-test in Excel” for help in creating a bar graph using Excel. You may also refer to
the “Creating a Bar Graph in Excel” PowerPoint under the Unit 6 Readings and
Resources.
Requirements:
• Answer all questions in Part A, B, and C.
• Submit a Word document with your answers.
Be sure to read the criteria below by which your work will be evaluated before
you write and again after you write.
Evaluation Rubric for t-Test Assignment
CRITERIA Deficient Needs
Improvement
Proficient Exemplary
0 points 20 points
Mean and
Standard
Deviation for
Weight Lost in
Pounds for the
Intervention
Group
The mean and
standard deviation
are not provided or
are inaccurate.
The mean and
standard deviation are
provided and
accurate.
0 points 20 points
Mean and
Standard
Deviation for
Weight Lost in
Pounds for the
Control Group
The mean and
standard deviation
are not provided or
are inaccurate.
The mean and
standard deviation are
provided and
accurate.
0 points 20 points
T-Test The result of the ttest (t statistic) is
not provided or is
inaccurate.
The result of the t-test
(t statistic) is provided
and is accurate.
0 – 14 points 15 – 16 points 17 – 19 points 20 points
Statistical
Significance
Either a statement
is not made as to
whether the
difference in
means scores is
statistically
significant and/or
an explanation is
not given as to
why the difference
is statistically
significant or not,
or the statement
and explanation
given are
incorrect.
Statement is made as
to whether the
difference in means is
statistically significant,
but no explanation is
given as to why the
difference is
statistically significant
or not.
Statement is made
as to whether the
difference in means
is statistically
significant, but the
explanation is
lacking detail.
Statement is made as
to whether the
difference in means is
statistically significant
and a thorough and
accurate explanation
is given as to why the
difference is
statistically significant
or not.
0 points 1 – 11 points 12 – 19 points 20 points
Bar Graph of
Mean Scores
for the
Intervention
Group and the
Control Group
Graph of mean
scores is not
provided.
Graph is provided but
does not accurately
illustrate the difference
in means scores
between each group.
Graph title and axes
Graph is provided
and accurately
illustrates the
difference in means
scores between
each group. Graph
is missing some
Graph of means is
provided and
accurately illustrates
the difference in mean
scores between each
group. Graph includes
CRITERIA Deficient Needs
Improvement
Proficient Exemplary
are provided but
mislabeled.
important
components, such
as a title or labeled
axes.
a title and labeled
axes.
