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                Images] Research II: Looking for Links; Evaluating Research-Flaws, Placebo

Looking For Links: Descriptive/Correlational Research

Descriptive/Correlational research can tell us if there is a link between variables, but not about cause/effect relationships

  • Do overweight people exercise less than normal weight people? (weight vs. exercise)
  • Do people in the South live fewer years than people in the North? (location vs. life expectancy)
  • Do angry people have more heart attacks than peaceful people (emotion vs. heart disease)
  • Do step-fathers treat their step-children worse than their natural children (biological relatedness vs. parental care)
  • Do more hours of athletic practice lead to more successful athletic performance? (practice vs. success)

Correlation coefficient: A numerical index between -1 and +1 which expresses the strength of relationship between two variables (correlation coefficient is labeled "r")

[Negative Correlation] {Zero Correlation] [Positive Correlation]
 Correlation (r) = -1.00   Correlation (r) = +0.05  Correlation (r) = +1.00 
* N = neuroticism, E = extraversion, O = openness to experience, A = agreeableness, C = conscientiousness

As a correlation moves from 0.0 toward +1.0 (more positive), the strength of the relationship increases. Similarly, as a correlation moves from 0.0 toward -1.0 (more negative), the strength of the relationship increases. Correlations near a value of 0.00 indicate that there is little to no relationship between two variables.

Hence, the correlation -0.90 is larger/stronger than the correlation +0.75.   
Correlations say that there is a relationship, NOT that one variable CAUSES the other. It is possible that both variables are actually caused by a third or fourth variable.

Other forms of Descriptive Research


Flaws: Evaluating Research

Sampling Bias: Is the sample representative of the population under review?

  • Who is supposed to be represented in your study, that is, to whom is this study supposed to generalize?
  • Bias can be introduced by
    • Using convenience samples (your friends, your family, etc.) to serve as participants
    • Using any non-random mechanism by which to assign participants to experimental conditions, for example, using the alphabet to assign participants, calling for volunteers, etc.   
    Consider the infamous 1936 Literary Digest "poll" which predicted that Alf Landon would beat Franklin D. Roosevelt in the presidential election by 57% to 43% (and win a landslide 370 electoral votes!) The magazine had contacted 10 million Americans (whose names were drawn from long lists of people who owned cars or telephones). The magazine got back over 2 million responses. Of course, in the actual election, Roosevelt beat Landon by 61% of the votes (523 electoral votes vs. 8 electoral votes for Landon).
    What did the Literary Digest do wrong?
    • Used a biased sample: in the midst of the Great Depression, many more rich people owned cars and telephones than poor people
    • Used a voluntary sample: people who were angry at Roosevelt's first term were more likely to send in a postcard ballot to the magazine than those who weren't angry.

      See The First Measured Century (PBS): George Gallup and the Scientific Opinion Poll

Placebo Effects: Changes in a person's behavior which come from the EXPECTATION of change, rather than the ingredients or components of the treatment they receive.

  • Research has shown that these effects can be quite strong.

  • "Nocebo" Phenomenon: Averse effects or negative changes in behavior (health, outcome, etc.) after taking a placebo.

Distortions in Self-Report Data: Bias introduced by participants who respond in ways that do not reflect their actual behavior, beliefs, judgments, etc.

  • Social Desirability: Give answers which reflect favorably on yourself
    • Willingness to admit small mistakes, common human failings, etc. VS. trying to appear perfect, for example,
      • I've never told a lieTrue or False?
      • I've always done my homework on timeTrue or False?
      • I always complete the readings for my college classes ahead of timeTrue or False?
    • You can download the Crowne & Marlow Social Desirability Scale in pdf format and score yourself.
  • Misunderstood or poorly worded questions
  • "Response sets" = participant responds in a stereotypical or automatic ways

    • Halo Effect: this is the tendency to rate someone or something positively (or negatively) on many different items from knowledge about one item. For example, you see someone help carry the groceries for an elderly person and conclude that the person is also trustworthy, friendly, and a hard worker.

    • Leniency-Severity-Generosity Effects

    • Extremist or Central Tendency response set: rate everything as terrible or excellent, or as average 

Experimenter Bias: Bias introduced when a researcher's expectations or preferences influence the outcome of the research. This may be done without the research ever realizing that he/she is affecting the outcome.

  • "Double-blind" Research: (the GOLD standard) In such an approach to research, neither the participants nor the data collectors know which participants are in the experimental group or in the control group.


Looking at Ethics

Psychology studies human beings and we humans are a very complex reality to study. We are often smart enough to understand the purpose of a research study in ways that would make that study invalid. Experimenters try to get people to respond honestly, but participants might distort their responses for any number of reasons.

In the last class, I gave you an example of researching whether faculty members might have an unconscious bias against women. Notice that the participants were not told that they were being studied for bias before their responses were collected. Indeed, if you asked the participating faculty directly, they would almost certainly have denied that they had any bias whatsoever. So, the experiment disguised how bias was going to be measured by NOT telling the participants what the independent variable was, that is, the applicant was either male or female. Is such deception justifiable or ethical?

The question of deception

Animal Research

Ethical Principles in Research with Human Subjects


Downs, A.C., & Lyons, P.M. (1991). Natural observations of the links between attractiveness and initial legal judgments. Personality and Social Psychology Bulletin, 17, 541-547.


This page originally posted on 1/28/04 and updated on Oct. 4, 2016