These study tips are designed to clarify key points and help you to avoid errors that students commonly make. Review the Tips for Success as you study each chapter and review them again after you have studied each chapter.

1. If you are reading this chapter prior to having studied Chapters 3 through 7, you should not read the material in this chapter on the significance of a correlation coefficient or on effect size or power.
2. If you’re in any way unsure about what a numeric equal-interval variable is, be sure to review the Chapter 1 material on kinds of variables.
3. When making a scatter diagram, it is easiest if you use graph paper.
4. When changing raw scores to deviation scores, it is easiest (and you will make fewer errors) if you do all the deviation scores for one variable and then all the deviation scores for the other variable. Also, to make sure you have done it correctly, when you finish all the deviation scores for a variable, add them up – they should add up to 0 (within rounding error).
5. If you calculate a correlation coefficient to be larger than +1.00 or less than -1.00, you have made a mistake (so go back and check all of your calculations)!
6. When changing the raw scores to deviation scores, it is easiest (and you will make fewer errors) if you do all the deviation scores for one variable and then all the deviation scores for the other variable. Also, to make sure you have done it correctly, when you finish all the deviation scores for a variable, add them up – they should add up to 0 (within rounding error).
7. If you feel you need some extra practice figuring a correlation coefficient, add the scores for this extra person to the scores shown in Table 11-1 and verify that the correlation is now indeed r = -1.8.
8. Do not read the section on Significance of a Correlation Coefficient if you have not studied Chapters 3 through 7.
9. Do not read the section on Effect Size and Power for the Correlation Coefficient if you have not studied Chapters 3 through 7.