Everyday Research Methods

Malnutrition statistics in North Korea

This Wall Street Journal article describes how a team of U.S. and European professors traveled to North Korea to teach students there about quantitative methods for studying their population.

North Korea, the story says, has "some of the least reliable statistics in the world."

Please take a look at the pop-out map of North Korea in this story.  The map shows the estimated rates of child malnutrition in each of North Korea's provinces. For example, it shows that the estimated rate of child malnutrition in the province of Jagong was 9.8%. That is a frequency claim: a claim about a single variable--the rate of malnutrition--in each province.

The caption on the map is worth attending to from a research methods perspective. The caption reads,

Researchers in North Korea often face challenges. In this 2012 study of child malnutrition, conducted with the support of three U.N. agencies, local village leaders chose the children from which researchers drew their subjects, so they could have excluded the most malnourished kids.

This first part of the caption describes a potential problem with the external validity of this claim. If officials did in fact select only the most healthy kids for the sampling frame, then the estimate of the true rate of child malnutrition would be too low.

Here's the second part of the map's caption:

And the data were collected at the end of the harvest, possibly producing a temporary uptick in nutrition levels.

You could say that this part of the caption is describing a potential problem with the construct validity of this claim. By measuring child malnutrition during a time of plenty, officials did not get a valid measure of the true health of the kids in the sample.

What lessons do you think the instructors are teaching to the students in North Korea?

 

Trashing your thoughts reduces their power

Another article from the mindfulness desk, this time graphable as an interaction.  Read on.

A recent study by psychologist Richard Petty and his colleagues investigated the situations in which people's thoughts have more power over them. Specifically, they wanted to know if thoughts would affect people less when they wrote them down and then threw them away--as in literally, in a trash can! Here's how the study was covered by the Huffington Post.

This study is a factorial design. Read the journalist's description below very carefully, attempting to locate the two independent variables and the dependent variable. 

[The first experiment] included 83 high-schoolers in Spain who were given three minutes to write their negative or positive thoughts about their own body image.

After writing down these thoughts, all of them were asked to read them back over and think about them. Half of them were then asked to throw away those written thoughts in the trash, while the others were not instructed to throw away their thoughts and were instead asked to proof-read what they had written. Then, researchers had the study participants rate their attitudes on their own body image on a scale -- for example, if they liked or disliked their bodies, thought they were attractive or unattractive, etc.

Researchers found that for the students who were not asked to throw away their written thoughts on their self-body image, what they had written down seemed to have an effect on how they rated their body image afterward. For example, someone who wrote down a lot of positive thoughts about themselves were likelier to rate themselves higher on the body image scale.

However, for the students who were asked to throw away their written thoughts, what they wrote down didn't seem to have any effect on how they rated themselves afterward.

a) What are the two IV's in this study?  Name each IV. Then list the levels of each IV. Are the levels of each IV manipulated as independent groups or within-groups?  

b) What is the main DV in this study?

c) Sketch a graph of the outcome of this study.

d) Estimate the main effects and interactions that Petty and his colleagues probably obtained.

The journalist also describes a second study in the paper. Here's the journalist's description:

 Some of the study participants were then asked to drag that file into the computer's recycling bin; others were instructed to just drag the file to a storage disk. Some of them were also asked to just imagine that the file was moved to the recycling bin.

The researchers found that those who actually dragged the file to the recycling bin were less affected by the thoughts they'd typed out, compared with the ones who just saved to them another disk, or those who just imagined moving them to the recycling bin.

e) The study above is a conceptual replication of the first. Instead of using a real trash can to operationalize the concept of "trashing," they used a virtual one--on a computer. Can you think of another way to operationalize "trashing?"

 f) The blogger's description of this second study is much less detailed than the blogger's description of the first. What details are left out of this description?

 

Suggested answers

a) The first IV is whether people wrote about positive or negative thoughts. It has two levels (positive or negative) and is independent groups.

The second IV is whether people proofread what they wrote or threw it in the trashcan. It has two levels (proofread or trash) and is independent groups.

b) The DV is body image, operationalized by a body image scale.

c) Based on my reading of the results, the graph might look something like this:

If your library has access to the journal Psychological Science, then you can look up the real graph of the results for this study. The study shows them in Figure 1.

d) The graph I sketched shows a probable main effect for the variable thought type, such that positive thoughts lead to higher body image than negative thoughts. There is probably no main effect for the trashed vs. proofread IV. There is an interaction, such that when people trashed their thoughts, positive messages led to only a little more positive body image than negative ones; but when people did not trash their thoughts, positive messages led to a lot more positive body image than negative ones.

e) Another way to operationalize "trashing" might be with a paper shredder, or by burning the paper you write your thoughts on. What are your ideas?

f) The second study description doesn't mention what topic participants wrote about (body image again? or something new?). The article mentions one IV (which has three levels--whether people dragged the file to the recycle bin, dragged it to the save icon, or just imagined dragging it to the recycle bin). But the article doesn't mention if there was another IV (such as positive vs. negative thoughts). It also doesn't mention how they operationalized the DV--they just say it was about being "affected by the thoughts." You can read the original published article in Psychological Science to look up these details (see p. 5).