CORRELATION

Direct relationships (positive correlations) exist when high scores on one variable are associated with high scores on another variable, as when intelligence is positively correlated with grade point average. Inverse relationships (negative correlations) exist when high scores on one variable are associated with low scores on a second variable, as when the amount of sleep one gets is negatively correlated with levels of irritability and anxiety.

Demonstrating that a correlation exists does not prove that changes in one variable are the cause of changes in the other, partly because other factors which are undetected may be influencing both known variables. Thus, knowing that a correlation exits may lead to two or more different interpretations of the correlation. For the studies described below, decide whether the correlation is positive or negative and give two explanations for the finding.

Type of correlation:  Positive

One explanation:  Smoking is often correlated with a lower socio-economic groups.  These same groups are less likely to have the economic opportunities for child development available to other groups. 

2. The more psychology courses students take during their college years, the higher scores they get on a measure of interpersonal sensitivity.

Type of correlation:  Positive

One explanation:  The longer anyone goes to college, the better they get at interpersonal sensitivity - but psych courses especially will help since they try to further our understanding of why people behave the way they do. 

3. A study on the effects of alcohol found that higher and higher doses of alcohol produced increasingly lower scores on a test of memory recall.

Type of correlation: Negative

One explanation:  Science has shown that the consumption of alchohol kills brain cells and impairs memory and judgement in the brain.  People just think they are smarter when they are drunk (impaired judgemnet again!)

4. A college professor notices that the farther students sit toward the back of the room, the worse their grades in the course seem to be.

Type of correlation: Negative

One explanation: any number of factors could explain this - students in the back are more distracted by what goes on in front of them, or those with learning difficulties or concentration issues are often relegated to the back of the room.  It also could be due to the teacher concentrating on the students in the front of the room and not giving enough attention to the students in the back of the room. 

5. When the physical attractiveness of high school girls was rated by their peers, it was noticed that those with the highest scores tended to do the best on a measure of self-esteem on record in the guidance office.

Type of correlation: Positive

One explanation: People talk to each other - especially high school girls.  If one girl is deemed pretty by their peers, it's highly probable that they know this - thus boosting self esteem. 

6. A survey of adolescents being treated for eating disorders noted that those who watched the most TV during the week tended to receive the lowest ratings on a measure of general health.

Type of correlation: Negative

One explanation: Well documented studies as well as anecdotal evidence from parents show that when kids watch a lot of TV they are less active - thus less healthy.  (They also tend to munch on a lot of junk food while they watch) 

7. In a study of suburban communities, it was noticed that communities that sex-related crimes was highest in the communities that had the largest number of X-rated adult book stores.

Type of correlation: Positive

One explanation: A community which will economically support an adult book store will also support  other sex-related activities like prostitution. 

8. A survey reveals that college students who eat breakfast regularly have a higher GPA than those that don't eat breakfast regularly.

Type of correlation: Positive

One explanation: Good nutrition helps the developing brain function better.  It's also hard to concentrate when you are hungry.

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Inquiries to: michael.connelly@kcmetro.edu
Last modified: 03/02/04