Bit More About t-Tests

Assume that the t you calculated was a person. If that score is close to the mean of the t distribution, it is not significant; there are too many scores hanging around the mean to make it special. But if your calculated score is at one extreme of the distribution, this would be usual (or in stats terms: “significant”), and the relationship between your score and the t distribution might look like this:

     When subjects are randomly assigned to groups, the t-test is said to be independent. That is, it tests the impact of an independent variable on a dependent variable. The independent variable is dichotomous (yes/no; treatment/control; high/low) and the dependent variable is continuous. If significant, the independent t-test supports a strong inference of cause-effect.

     When subjects are given both conditions (both means are measures of the same subjects at different times), the t-test is said to be dependent or correlated. Because it uses repeated measures, the correlated-t is often replaced by using a regression (where the assumptions of covariance are more clearly stated).

NOW YOU CHOOSE:
    Day 8: Student’s t-Test
    Bit More About t-Test
    Even More About t-Test
    How to Calculate t-Test
    Practice Problems
    More Practice Problems
    Word Problems
        Sim1           Sim2            Sim3
        Sim4           Sim5            Sim6
        Sim7           Sim8            Sim9
    Basic Facts About t-Test
    Vocabulary
    Formulas
    Quiz 8
    Summary