Everyday Research Methods

Don't miss this piece on means!

Here's a thoughtful editorial from NYT on averages.

The author, Stephanie Coontz, gives some nice examples of what outliers can do to a mean, and how extreme scores can mislead us about patterns in our data. Have fun reading it!

 

 

 

Can early math skills help you make money?

The Atlantic provides a clearly written summary of a recent longitudinal study. The headline reads:

Study: Math Skills at Age 7 Predict How Much Money You'll Make

According to the summary, the researchers measured kids' IQ, math skills, reading skills, and SES (Socio-economic status) at age 7, and then measured their income at age 42.

They found that

How much money the people made at midlife was predicted by math ability at age seven. The other factors may have helped them on the path to success, but even when those were controlled for, the association between basic math and reading skills and future socioeconomic status remained, and remained significant...

Do you notice how this description uses the key phrase, "even when those were controlled for..."?  This should signal to you that the researchers used multiple regression in their design.

a) What might the regression table have looked like in the study? What would the DV have been? What would the predictor variables have been?  Estimate what you think the beta might have been for the predictor, "Math skills at age 7" (that is, is it positive or negative? Significant or not?).

b) Suppose a critic reads this article and says, "I don't think that it's math skills--I think it's IQ. Smarter people just earn more money and they did better at math as kids--that's all." What should you say in response?  In this study, is IQ a potential third variable that could explain the association between math skills and future income?

c) Now suppose that a critic suggests that school quality might be a third variable. Kids who go to higher-quality schools had better math skills and also made more money. In this study, is school quality a potential third variable that could have explained the association between math skills and future income?

d) One part of the story says,

...How much money the people made at midlife was predicted, for girls only, by early reading ability.

Is this sentence describing a mediator? A moderator? Or a third variable?

 

 

Targets of prejudice manage impressions

How would you respond if you knew that people might stereotype you negatively? That's what one study recently asked. They wondered how people would approach a social situation if they were worried about the stereotypes the other person might have about them.

The studies in question can provide you with some handy practice on factorial designs. 

Scientific American wrote about the study by Rebecca Neel and her fellow researchers. They explain that they recruited 75 college students, some of whom were overweight and some of whom were not.

In the first study, the participants answered questions about obese people and other stereotyped groups.  Scientific American continues:

The students also were asked to envision meeting someone new and then to choose how they'd make a good impression from options such as arriving on time, wearing clean clothes, smiling and looking relaxed. Some students answered the group [stereotype] questions first so they'd have group-related stereotypes in mind when they got to the first-impressions' questions. Others completed the study the other way around.

The results showed that thinking about stereotyping changed people's behavior. Overweight students who'd first answered questions about  obese people were more likely than other participants to rank "wearing clean clothes" as a very important way to make a good first impression. Normal-weight students and overweight students who hadn't been primed to think of stereotypes were more likely to prioritize arriving on time.

 a) For the study above, the dependent variable could be described as the degree to which participants prioritized wearing clean clothes (over arriving on time). In addition to this DV, there is an independent variable and a participant variable in this factorial design. What are they?

b) How many levels are there in each of the IV's/PV's?  Are these variables independent groups or within-groups?  What kind of design is it (use this format: ___ x ___)?

c) Sketch a graph of what the results are, as they are described in the paragraph above. What main effects and interactions are present in the graph that you sketched? 

 

 

The second study reported is also a factorial design. It is more difficult to find the IV's in this description, but give it a shot:

 

In a second study, researchers repeated the test with overweight men and black men. When prompted to think of stereotypes, overweight men ranked wearing clean clothes as the most important step toward making a good first impression. Black men, who are often stereotyped as violent and anti-social, prioritized smiling.

d) What are the IV's/PV's in this study? What is the dependent variable? (There seem to be two key dependent variables in this version of the study.)

e) Make two graphs of the 2x2 design above. One graph is for the first DV, and another graph should have the same IV's/PV's as the first graph, but will have the second DV on its y-axis.