Everyday Research Methods

What's correlated?

I recently ran across the blog, correlated.org, as well as a book that goes with it, called Correlated (both are by Shaun Gallagher). Every day, the author posts the results of a correlation that is based on survey data. The goal of the project is to entertain. Many of the correlations are amusing, such as the correlation between liking Disney movies and preferring lemonade to iced tea (see figure). 

The correlations on correlated.org are presented very differently from the ones in the textbook. The text shows you two ways to present correlational data: a scatterplot and a bar graph. You use scatterplots when both variables are quantitative, and you use a bar graph when one is quantitative and the other is categorical.

In contrast, correlated.org uses two pie charts to represent each of its correlations. But for some reason, pie charts are almost never used in psychology research.

Think about the two variables in the pictured correlation. The first variable (is your favorite animated movie a Disney movie?) is categorical--the answers are yes or no. Similarly, the second variable (do you prefer iced tea or lemonade?) is also categorical--the answers are iced tea or lemonade. When both variables are categorical, a scatterplot can't be used. Pie charts are one option, but bar graphs are  possible here too (and are more elegant, in a way, since you can use one bar graph in place of two pie charts).

Questions

a) Why does this count as a correlational study and not an experiment or a survey?

b) You can present the lemonade/Disney results as a single bar graph rather than a pie chart. Sketch it out for yourself.

c) Think about the causal direction of the lemonade/Disney results. Is it clear which of the two variables comes first in time? What third variables seem likely to be associated with both variables?

d) What are the advantages and disadvantages of using two pie charts versus one bar graph? Which one is easier to understand? Which one serves author Gallagher's purpose?

e) What questions would you ask to determine the external validity of this result?

 

Classifying claims about play

National Public Radio has a new series of stories on play in children and animals. In this report, they interview scientists who have studied how play affects the brain. 

The scientists in the interview do not go into much detail on the methods that they have used to study play. However, the article provides a good chance to classify claims.  For each of the following statements (each quoted from the story) a) is this a frequency, association, or causal claim? and  b) What are the variables in each claim? 

1. When ....rats are young, play appears to initiate lasting changes in areas of the brain used for thinking and processing social interactions, Panskepp says.

2. ... we found that of the 1,200 genes that we measured, about one-third of them were significantly changed simply by having a half-hour of play

3. Play also helps both people and animals become more adept socially, Pellis says.

4. ....the skills associated with play ultimately lead to better grades. 

5.  The experience of play changes the connections of the neurons at the front end of your brain

6. countries where they actually have more recess tend to have higher academic performance than countries where recess is less.

In addition to classifying these claims and variables, perhaps you can also propose the type of study (e.g., experimental or correlational) you would be looking for, to support each claim? 

Photo credit:  Aung Pyae Soe/National Geographic Creative 

 

Suggested Answers (Even numbered items)

2. This is a causal claim ("changed" is a causal verb). The variables are "whether or not a gene is changed" and "playing for 30 minutes or not"

4. This is a causal claim ("ultimately lead to" implies that )   The variables are "the level of skill associated with play" and "quality of grades."

6. This is an association claim ("tend to have" is an association phrase). The variables are "how much recess" and "level of academic performance."