Correlational Research Method

Correlation Positive correlation (between 0 and +1.00) Indicates a direct relationship, meaning that two things increase together or decrease together Negative correlation (between 0 and −1.00) Indicates an inverse relationship: As one thing increases, the other decreases. Correlation coefficient Provides a statistical measure of how closely two things vary together and how well one predicts the other

SCATTERPLOT FOR HEIGHT AND WEIGHT This chart displays data from 20 imagined people, each represented by a data point. The scattered points reveal an upward slope, indicating a positive correlation.

The slope of the dots suggests the direction Correlation Measure of the extent to which two events vary together, and thus of how well either one predicts the other. Correlation coefficient Mathematical expression of the relationship, ranging from −1.00 to +1.00, with 0 indicating no relationship. Scatterplot Graphed cluster of dots, each of which represents the values of two factors. The slope of the dots suggests the direction of the relationship between the two factors. How much the dots are scattered suggests the strength of the correlation (with little scatter indicating high correlation).

Indicate whether each of the following statements describes a positive correlation or a negative correlation. 1. The more children and youth used various media, the less happy they were with their lives (Kaiser, 2010). 2. The more sexual content teens saw on TV, the more likely they were to have sex (Collins et al., 2004). 3. The longer children were breast-fed, the greater their later academic achievement (Horwood & Ferguson, 1998). 4. The more income rose among a sample of poor families, the fewer symptoms of mental illness their children experienced (Costello et al., 2003). ANSWERS: 1. negative, 2. positive, 3. positive, 4. negative

Length of marriage correlates with hair loss in men Length of marriage correlates with hair loss in men. Does this mean that marriage causes men to lose their hair (or that balding men make better husbands)? Nancy Brown/Getty Images ANSWER: In this case, as in many others, a third factor can explain the correlation: Golden anniversaries and baldness both accompany aging.

THREE POSSIBLE CAUSE-EFFECT RELATIONSHIPS People low in self-esteem are more likely to report depression than are those high in self-esteem. One possible explanation of this negative correlation is that a bad self-image causes depressed feelings. But, as the diagram indicates, other cause-effect relationships are possible.