Chapter Outline

I. Chapter overview

II. Causality: The simple experiment's purpose

A. The logic of causality

B. Obstacles to establishing causality: The variability problem

C. Solving the variability problem

III. Basic terminology

A. Experimental hypothesis

B. Null hypothesis

C. Administering the independent variable

D. Experimental and control groups

1. The value of independence

2. The value of assignment

E. Collecting the dependent variable

F. The statistical significance decision

1. Statistically significant results

2. Null results

G. Summary of the ideal simple experiment

IV. Errors in determining whether results are statistically significant

A. Type 1 errors and their prevention

B. Type 2 errors

1. Preventing type 2 errors by increasing power

a. Reducing random error

1. Standardize procedures and use reliable measures

2. Use a homogeneous group of participants

3. Code data carefully

b. Let random error balance out

c. Create larger effects

C. Summary of the effects of statistical considerations on designing the simple experiment

V. Nonstatistical considerations

A. External validity versus power

B. Construct validity versus power

C. Ethics versus power

D. Ethics versus the simple experiment

VI. Analyzing data from the Simple Experiment: Basic Logic

A. Estimating what you want to know

1. Calculating sample means

2. Comparing sample means

B. Inferential statistics: Judging the accuracy of your estimates

1. Estimating the accuracy of individual sample means

a. Consider population variability: The value of the standard deviation

b. Consider sample size: The role of standard error

c. Using standard error

2. Estimating the accuracy of your estimate of the difference between population means

a. How differences are distributed: The large sample case

b. How differences are distributed: The small sample case

c. Interpreting results of a t test

d. Assumptions of the t test

C. Questions raised by results

1. Questions raised by nonsignificant results

2. Questions raised by significant results

VII. Concluding remarks

Summary

Key terms

Exercises


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