Take the McCroskey test yourself
to see your apprehension level
This PowerPoint will walk through the
comparison of means of the pre and
post-tests
McCroskey Scenario t-test
Remember the Types of Scales?
Nominal Data (Chi-square)
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classification data, e.g. m/f
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no ordering, e.g. it makes no sense to state that M > F
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arbitrary labels, e.g., m/f, 0/1, etc
Ordinal Data (t-test)
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ordered but differences between values are not important
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e.g., political parties on left to right spectrum given labels 0, 1, 2
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e.g., Likert scales, rank on a scale of 1..5 your degree of satisfaction
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e.g., restaurant ratings
Interval Data
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ordered, constant scale, but no natural zero
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differences make sense, but ratios do not (e.g., 30°-20°=20°-10°, but
20°/10° is not twice as hot!
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e.g., temperature (C,F), dates
Ratio Data
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ordered, constant scale, natural zero
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e.g., height, weight, age, length
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Quoted from http://www.stat.sfu.ca/~cschwarz/Stat301/Handouts/node5.html
McCroskey Scenario t-test
Take McCroskey's PRCA.
http://ww3.llcc.edu/speechsurvey/survey.aspx OR
http://www.jamescmccroskey.com/measures/prca24.
htm
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McCroskey Scenario t-test
Study
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Imagine that a group of 20 students enrolled in Dr. Cohn's public
speaking course. These students took McCroskey's test on the first
day of their public speaking course. Scores can range from 24120, and a score above 65 suggests higher than
average apprehension. Dr. Cohn is concerned that she has so many
apprehensive students in the class. Here are their scores:
After one term of instruction, Dr. Cohn administered the test at the
end of the course because she wanted to see if taking the course
lowered student apprehension.
In this case, there is a pre-post test for one group and the data on
a scale. Dr. Cohn asks you to calculate the results using a t-test.
Is there a significant difference in the communication apprehension
level of the class members before and after taking Dr. Cohn's
course?
McCroskey Scenario t-test
First, you enter the data.
McCroskey Scenario t-test
Pull down “Help,” select “Statistics
Coach” if you need help.
McCroskey Scenario t-test
Compare means of the pre and post
test.
McCroskey Scenario t-test
Select two
McCroskey Scenario t-test
Related data
McCroskey Scenario t-test
Normal Distribution
McCroskey Scenario t-test
The “Statistics Coach” help function
guides you in what statistical test to use.
McCroskey Scenario t-test
What are the means to be compared?
The average of the pretest, the average of the posttest. The calculator
will figure this automatically as part of the t-test calculation.
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Add the 20 scores from the pretest
= 1600
Divide by 20 students in the class =
80 is the average or mean for the
pretest.
Add the 20 scores from the posttest
= 1193
Divide by 20 students in the class =
51
McCroskey Scenario t-test
95% confident that the difference is not
by chance
McCroskey Scenario t-test
Enter Data
McCroskey Scenario t-test
From menu
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Select “Analyze”
Select “Compare Means,” which is
what a t-test does.
Select “Paired-Samples T Test,”
which is what the Statistics Coach
told us to do based on our answers
to the various questions.
McCroskey Scenario t-test
McCroskey Scenario t-test
If you don’t have SPSS, here is a calculator:
http://www.physics.csbsju.edu/stats/ttest_bulk_form.html
McCroskey Scenario t-test
McCroskey Scenario t-test
The standard deviation helps the
researcher determine how much
distance from the mean is typical and
how much is considered significant.
McCroskey Scenario t-test
Using unpaired t-test
t= 4.46
sdev= 20.2
degrees of freedom = 38
The probability of this result, assuming the null hypothesis,
is less than .0001
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Scores are significantly lower after the
course. (Remember, this is fictional
research.)
We can feel confident that completing the
public speaking course helped lower
student communication apprehension.
McCroskey Scenario t-test
Hope you enjoyed this
application practice!
McCroskey Scenario t-test