1. Part IV Significantly Different: Using Inferential Statistics
Chapter 11   
t(ea) for Two:
Tests Between the Means of Different Groups

2. What you will learn in Chapter 11
When to use a t test
How to compute the observed t value
Interpreting the t value and what it means

3. t Test for Independent Samples
Determining the correct statistic

4. Computing the Test Statistic
Numerator is the difference between the means
Denominator is the amount of variation within and between each of the two groups

5. Degrees of Freedom The degrees of freedom approximates the sample size
Degrees of freedom can vary based on the test statistic selected
For this procedure…
n1 – 1 + n2 – 2

6. So How Do I Interpret… t (58) = -.14, p > .05
t represents the test statistic used
58 is the number of degrees of freedom
-.14 is the obtained value (from the formula)
p > .05 indicates the probability

7. Special Effects…
Effect size is a measure of how different two groups are from one another
Standardized difference between two group means
Jacob Cohen

8. Computing Effect Size Small = 0.0 - .20 Medium = .20 - .50
Large = .50 and above

9. Effect Size Calculatorm

10. Using the Computer
Computing a t Test using SPSS

11. SPSS Output
What does it all mean?

12. Glossary Terms to Know Degrees of freedom t Test Effect size
Independent t Test
Obtained value
Critical value
Effect size

13. Part IV Significantly Different: Using Inferential Statistics
Chapter 12   
t(ea) for Two (Again):
Tests Between the Means of Related Groups

14. What you will learn in Chapter 12
When to use a t test for dependent means
How to compute the observed t value
Interpreting the t value and what it means

15. t Test for Dependent Samples
Determining the correct statistic

16. Computing the Test Statistic
Numerator reflects the sum of the differences between two groups

17. Degrees of Freedom The degrees of freedom approximates the sample size
Degrees of freedom can vary based on the test statistic selected
For this procedure…
n – 1 (where n is the number of observations)

18. So How Do I Interpret… t (24) = 2.45, p > .05
t represents the test statistic used
24 is the number of degrees of freedom
2.45 is the obtained value (from the formula)
p > .05 indicates the probability

19. Using the Computer
SPSS and Paired Samples t Test

20. SPSS Output
What does it all mean?