Chapter 9

I. t-test for single samples

A. Assumptions for t-test.

B. standard error for t-test

C. Formula for t-test

D. Degrees of freedom df : number of scores free to vary

n - 1

II. t distributions

Unlike the normal distribution, there are an infinite number (family) of t distributions: one for each value of df (Table B.2, p. A-27).

A.Shape -

B. Central tendency -

C. Spread -

(Fig. 9.1 overhead)

D. Proportions differ with df. See Table B.2

(Table B.2 overhead)

III. Steps in hypothesis test using t

Same as with z

A. State hypotheses

B. Set alpha

C. Collect data and perform statistical test

D. Make decision about Ho:

E.Reporting result in APA format (only need to report type (directional or nondirectional) of hypothesis test if it is directional).