1. Discovering Psychology Special Update For DSM-5
Don H. Hockenbury and Sandra E. Hockenbury
Discovering Psychology
Sixth Edition
Special Update For DSM-5
Appendix A
Statistics: Understanding Data
Copyright © 2014 by Worth Publishers

2. Table A.1 A Frequency Distribution Table
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

3. This histogram is another way of presenting the data given in Table A
This histogram is another way of presenting the data given in Table A.1. Like the table, the histogram shows that most people do, at best, only a moderate amount of aerobic exercise (two hours or less each week). This is immediately clear from the fact that the highest bars on the chart are on the left, where the hours of exercise are lowest.
Figure A.1 A Histogram
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

4. Figure A.2 A Frequency Polygon (Positive Skew)
Like Table A.1 and Figure A.1, this frequency polygon shows at a glance that the number of hours of aerobic exercise weekly is not great for most people. The high points come at one and two hours, which doesn’t amount to much more than 10 or 15 minutes of exercise daily. An asymmetrical distribution like this one, which includes mostly low scores, is said to be positively skewed.
Figure A.2 A Frequency Polygon (Positive Skew)
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

5. Figure A.3 A Frequency Polygon (Negative Skew)
When more scores fall at the high end of a distribution than at the low end, the distribution is said to be negatively skewed. We would expect a negatively skewed distribution if a health-promotion program worked and encouraged more hours of aerobic exercise. The more effective the program, the greater the skew.
Figure A.3 A Frequency Polygon (Negative Skew)
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

6. Figure A.4 Distributions with Different Variability
Two distributions with the same mean can have very different variability, or spread, as shown in these two curves. Notice how one is more spread out than the other; its scores are distributed more widely.
Figure A.4 Distributions with Different Variability
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

7. Table A.2 Calculating the Standard Deviation
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

8. Figure A.5 The Standard Normal Curve
The standard normal curve has several characteristics. Most apparent is its symmetrical bell shape. On such a curve, the mean, the median, and the mode all fall at the same point. But not every curve that is shaped roughly like a bell is a standard normal curve. With a normal curve, specific percentages of the distribution fall within each standard deviation unit from the mean. These percentages are shown on the graph.
Figure A.5 The Standard Normal Curve
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

9. Figure A.6 Scatter Plot of a Positive Correlation
A correlation (or the lack of one) can be clearly shown on a scatter diagram. This one shows a moderately strong positive correlation between subjects’ compliance with the yoga component of the alternative health-promotion program and their energy level. The positive direction of the correlation is indicated by the upward-sloping pattern of the dots, from bottom left to top right. This means that if one variable is high, the other tends to be high, too, and vice versa. That the strength of the relationship is only moderate is indicated by the fact that the data points (each indicating an individual subject’s score) are not all positioned along a straight diagonal line.
Figure A.6 Scatter Plot of a Positive Correlation
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

10. Figure A.7 Scatter Plot of a Negative Correlation
In general, people who engage in meditation more often tend to smoke less. This negative correlation is indicated by the downward-sloping pattern of dots, from upper left to lower right. Because these dots are clustered somewhat closer together than those in Figure A.6, we can tell at a glance that the relationship here is somewhat stronger.
Figure A.7 Scatter Plot of a Negative Correlation
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

11. Figure A.8 Scatter Plot of No Correlation
You may be surprised to learn that in this study, compliance with the aerobic exercise portion of the traditional program was not related to level of coping. This scatter diagram shows that lack of relationship. The points fall randomly, revealing no general direction or trend and thus indicating the absence of a correlation.
Figure A.8 Scatter Plot of No Correlation
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers

12. Figure A.9 The Standard Normal Curve
Don H. Hockenbury and Sandra E. Hockenbury: Discovering Psychology, Sixth Edition – Special Update For DSM-5 Copyright © 2014 by Worth Publishers