On Variability

An important part of research methods is understanding concepts in measurement. Those include central tendency and variability. Of these, variability is more probably difficult to understand.

A couple of recent articles have highlighted the long-running longitudinal study, funded by W.T. Grant. One of those, in The Atlantic details many of the facets of his longitudinal study. Another, in the New York Times summarizes the work.

The study is remarkable because the 268 students were specially selected from the Harvard University classes of 1942, 1943, and 1944 for being among the most well-adjusted members of those classes (in other words, selected for their relative LACK of variability). Yet, over the years the life trajectories diverged incredibly. One member (John F. Kennedy) became president while another died after falling down a set of stairs, drunk.

Psychology is complex and individuals who may seem similar at one point in their lives may diverge from each other later for a wide variety of reasons. Finding those reasons is a goal of research.

Race/Ethnicity: Operational Definitions?

A recent article in the Chronicle of Higher Education highlights the research of Inkelas, Soldner, and Szelenyi. They tested three approaches other researchers use to classify race or ethnicity.

The three approaches tested were:

• Classify as biracial or multiracial
• Classify multiracial persons as the least common of categories selected
• Classify according to OMB categories

Their findings indicated that how researchers classified race or ethnicity could profoundly affect the results.

To us, this type of classification is an example of the importance of the operational definition. Recall our discussion of operational definitions on pp. 95-97 in chapter 4. On page 97, we write:

• In the Know: Perhaps the most important step you can take if you want to move from confusion to confidence about a scientific topic is to find out how the concepts are measured. Knowing how schizophrenia, intelligence, or subjective well-being is measured gives you a big boost toward understanding the topic.

To that, we add that race and ethnicity are not easy to operationally define. Thus, one should be very cautious when comparing studies on those variables. Be sure YOU know what operational definitions the authors are using for race and gender.

Breaking Down Research Designs

After a less-than-stellar set of test grades on chapters 7 and 8, I decided to re-explain the characteristics of research design. The test question was:

What is a design? What are its components?

In chapter 2, we state (p. 44): "The design of a research project includes the number of groups, how they are treated, and how the behavior is measured. The dependent variable, the independent variable, levels of the independent variable, and how extraneous variables are controlled are all aspects of research design."

In chapter 7, we introduce between-subjects designs and the extraneous variables of selection, differential attrition, and diffusion of treatment. In chapter 8, we introduce within-subjects designs and the extraneous variables of testing, instrument change, history, maturation, and regression (to the mean).

Let's break down design even further.

RESEARCH Type

• Experiment
• Quasi-experiment
• Field Study
• Naturalistic Observation
• Participant Observation
• Case Study
• Interview
• Focus Group
• Oral History
• Archival Study
• Small N Study
• Other
  

NUMBER of Groups (N)

• One
• Two
• Three
• Four
• More

GROUPS

• Between Subjects
• Within Subjects
• Mixed

VARIABLES

• Independent (number, levels)
• Dependent (number, quantitative or qualitative, continuous or discrete)
• Extraneous (how controlled or not)

EXPLORATORY DATA ANALYSIS & STATISTICS

• Graphs
• Descriptive Statistics
• Correlations
  
• Confidence Intervals
• NHST Tests and Significance (e.g., t-test, ANOVA, chi-square)
  
• Nonparametric Tests (e.g., Mann-Whitney, Wilcoxon Matched-Pairs Signed Ranks, Spearman correlation coefficient)
  
• Effect Sizes

CONTROLLING EXTRANEOUS VARIABLES

• Via design
• Via procedures

ETHICS

As we note in chapter 3, any design that fails to properly follow the current ethical standards is, by definition, a bad design.

So, there are many aspects to research design. Careful researchers devote much time toward perfecting their design and then pilot testing it before collecting data for real.

The Kilo in Crisis

Here's a recent story from the Los Angeles Times.

It tells about how the various standard kilograms around the world are no longer standard. When these kilogram weights were checked against the standard kilogram in Paris (made of platinum-iridium), they no longer weighed the same.

Here is a link to a picture of the standard kilogram. The kilogram is the last physical standard that is still defined in reference to a physical object. Originally, the kilogram was defined as the mass of a cube of water with sides equal to 10 centimeters. No one knows why the standard kilograms are losing weight, but the loss has led to a search for alternative standards. One approach is to construct a very sensitive magnetic balance, another is to actually count the atoms of a particular element.

All other standard units are defined in other ways, without reference to physical objects. The National Institute of Standards and Technology (NIST) defines the other standards. CLICK HERE to see all of their definitions and the historical context that led to the definitions. The NIST's definitions of the meter, the second, and the candela are reproduced below.

"The meter is the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second." Originally, the meter was defined as 1/10,000,000 of a quarter of the earth’s circumference.

"The second is the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the Cesium 133 atom." Originally, the second was defined as 1/86,400 of the mean solar day.

"The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian." Originally, the candela was the light given off by a standard candle (candela is Latin for candle).

One of the fundamentals of science is measurement. As sciences became more and more developed, the need for precision became more acute. So, redefining the kilogram is a real crisis is science.

Children and Sleep Loss: Recent Research

This blog entry has several purposes. One is to highlight recent research on sleep loss and its effects. Another is to illustrate some of the research techniques used to document the effects of sleep loss.

A recent article in New York Magazine inspired this entry. Here's the link to that article. The article references survey research conducted by the National Sleep Foundation. Basically, children are sleeping less than they did 30 years ago. Very few (5%) high school seniors get eight hours sleep a night. The average sleep time for them is about six and a half hours. Here's a link to an article about this research.

Avi Sadeh, a researcher at Tel Aviv University, conducted a sleep study where he asked 4th and 6th graders to either sleep a little more or sleep a little less each night for three nights. The children were randomly assigned to either group.

Sadeh was worried that his treatment (which was about a half hour of more sleep or less sleep each night) would not be enough to detect. The dependent variable he used, a test of neurobiological functioning, detected large differences because of sleep loss. The sleepy sixth graders functioned worse than normal fourth graders. See: The effects of sleep restriction and extension on school-age children: What a difference an hour makes. Child Development, 74, 444-455. Sadeh need not have worried about his design. One hour made a big difference.

Much other research supports the relationship between sleep loss and academic problems. In response, some school districts are moving the start of the school day to a later time. Two school districts, one in Minnesota and one in Kentucky reported amazing results. In Minnesota, SAT scores went up. In Kentucky, driving accidents for teens went down.

Response to these data has not been what you might expect. Only a few school districts have started school later. Not many parents have made their children sleep more. The bottom line? We all need more sleep.

Sweat equity

I could not resist--research on sweat. It's true, research topics ARE all around us. (Apparently, some of them are even ON us.) Maybe it's the fact that today's temperatures here were well over 100 degrees F that has grabbed my attention.

Again, the New York Times has inspired me to post with an article titled: Sweatology.

There are some interesting facts in that article:

• Humans tolerate cooling more than they tolerate heating
• People show tremendous variation in the number of sweat glands they possess
• Our body temperatures are lower in the morning.
• Thermoregulation in menopausal women goes awry so that they believe they are hotter than they really are and they sweat more.
• The elderly sweat less than they should (physiology again) and thus are more prone to heat related problems.
• Anger, too, makes us sweat.
• Clothing affects sweating. Naked people sweat more than clothed people. (The IRB is going to love that one.)
  
• Heat acclimation is a real phenomenon. After being in the heat for a week or so, people's sweat glands get bigger and produce more sweat.

Here are the researchers mentioned in the article.

Nina Jablonski is an evolutionary anthropologist whose recent book, Skin, compares the cooling strategies of various primate species (among other topics).

Craig Crandall studies human thermoregulation and has a lab in Dallas.

The National Renewable Energy Laboratory has developed a manikin called Adam, to measure human thermal comfort inside automobiles. Their goal is to decrease fuel consumption by reducing the use of automotive air conditioning.

Edison once said, "Genius is 1% percent inspiration and 99% perspiration." Maybe he was right.

Perception and Highway Signs

Martin Pietrucha is an associate professor of civil and environmental engineering at Penn State University. His research focuses on the readability of highway signs. He lists human factors as one of his specialties.

A recent New York Times article highlights his research on a new font, Clearview, with improved readability. The Federal Highway Administration approved Clearview in 2004. Many states are now replacing their older Highway Gothic font signs with Clearview.

Here is a picture of two signs. The left one is in Highway Gothic and the one on the right is in Clearview.
Graphic source

Here is how these data are collected:


Graphic source

Future research of this type will look at negative contrast signs (dark on light).

The research described here and other similar human factors research are examples of how psychologists and other scientists can apply the principles of measurement and research to solve real world problems.

Test-Retest

It's hard to find stories on statistical and methodological topics. Here's one such rare story.

The New York Times ran a poll (N = 1,554, Sampling error = + or - 3%) on Hillary Clinton in early July, 2007. One question, "Looking back, do you think the United States did the right thing in taking military action against Iraq, or should the United States have stayed out?"

The results surprised the pollsters because more respondents agreed with the question (42%) in July compared to respondents to the same question (35%) in a May poll. All of the other war-related questions had shown no such change.

The pollsters finally concluded they needed to retest the question. The did so after removing a question about Clinton's repudiation of her 2002 vote against the war. In the original poll, that question was near the military action question.

The second poll (N = 889, Sampling error = + or - 3%) produced nearly identical results with 42% agreeing. In this second poll, another question also showed a change from the earlier May data. Fewer respondents (66%) thought that "things are going badly for the United States in its efforts to bring stability and order to Iraq" than in May (76%). After running the second poll, the pollsters were confident they had detected a change in public opinion. However, they did not know what was causing the change.

Here is a link to the New York Times story