1. University of Massachusetts at Boston
T-TEST
Research Methods
University of Massachusetts at Boston
©2006 William Holmes

2. T-TEST: COMPARING TWO GROUP MEANS
Set criterion (alpha level).
Check group frequencies, means, and standard deviations.
Compare means for each group.
Examine t-value, degrees of freedom, and significance probability.
If probability smaller that alpha level, difference is significant.

3. EXAMPLE 1: t-test Mental Health by Sex
Males Females
Mean N
Std. Dev.
Difference of Means=2.1
Are women healthier than men?

4. EXAMPLE 1(cont’d.): t-test Mental Health by Sex
Males Females
Mean N
Std. Dev.
Difference of Means=2.1
t=1.89, d.f.=48, P=.06
Answer: Women are not healthier than men.