1. McCroskey Scenario t-test 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

2. McCroskey Scenario t-test Remember the Types of Scales? Nominal Data (Chi-square)  classification data, e.g. m/f  no ordering, e.g. it makes no sense to state that M > F  arbitrary labels, e.g., m/f, 0/1, etc Ordinal Data (t-test)  ordered but differences between values are not important  e.g., political parties on left to right spectrum given labels 0, 1, 2  e.g., Likert scales, rank on a scale of 1..5 your degree of satisfaction  e.g., restaurant ratings Interval Data  ordered, constant scale, but no natural zero  differences make sense, but ratios do not (e.g., 30°-20°=20°-10°, but 20°/10° is not twice as hot!  e.g., temperature (C,F), dates Ratio Data  ordered, constant scale, natural zero  e.g., height, weight, age, length  Quoted from http://www.stat.sfu.ca/~cschwarz/Stat- 301/Handouts/node5.htmlhttp://www.stat.sfu.ca/~cschwarz/Stat- 301/Handouts/node5.html

3. McCroskey Scenario t-test Take McCroskey's PRCA. http://ww3.llcc.edu/speechsurvey/survey.aspx OR http://www.jamescmccroskey.com/measures/prca24. htm http://ww3.llcc.edu/speechsurvey/survey.aspx Photo Source http://2.bp.blogspot. com/_27z_ybX1fcc/S afUfnpKgwI/AAAAAA AAAI4/nwRnSJx33dw /s400/speakerbestsel f.jpg

4. McCroskey Scenario t-test Study  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 24- 120, 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?

5. McCroskey Scenario t-test First, you enter the data.

6. McCroskey Scenario t-test Pull down “Help,” select “Statistics Coach” if you need help.

7. McCroskey Scenario t-test Compare means of the pre and post test.

8. McCroskey Scenario t-test Select two

9. McCroskey Scenario t-test Related data

10. McCroskey Scenario t-test Normal Distribution

11. McCroskey Scenario t-test The “Statistics Coach” help function guides you in what statistical test to use.

12. 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.  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

13. McCroskey Scenario t-test 95% confident that the difference is not by chance

14. McCroskey Scenario t-test Enter Data

15. McCroskey Scenario t-test From menu  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.

16. McCroskey Scenario t-test

17. If you don’t have SPSS, here is a calculator: http://www.physics.csbsju.edu/stats/t- test_bulk_form.html http://www.physics.csbsju.edu/stats/t- test_bulk_form.html

18. McCroskey Scenario t-test

19. The standard deviation helps the researcher determine how much distance from the mean is typical and how much is considered significant.

20. 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  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.

21. McCroskey Scenario t-test Hope you enjoyed this application practice!