research strategies in psychology. descriptive research strategies: the case study

Research Strategies in Psychology

Descriptive Research Strategies:

The Case Study


The Case Study

• “Given a thimbleful of [dramatic] facts we rush to make generalizations as large as a tub” - Psychologist Gordon Allport

» Fears after school shootings or kidnappings» The contradictory case: e.g. “My

grandfather smoked until he was 102” » Unreliability of anecdotal evidence


The Survey• Used in both

descriptive and correlational studies

• Asks people to report on behaviour and opinions.

The Survey:

Wording Effects• Should cigarette ads or pornography be

allowed on television?• People prefer “not allowing” to “forbidding” or

“censoring”• Only 27% of Americans approved of “government

censorship” of media sex and violence, while 66% approved of “more restrictions on what is shown on television”

• People prefer “aid the needy” to “welfare”• EI instead of UI

The Survey:

Sampling• False consensus affect

• A “sample” is a small group selected randomly to represent the larger population

• The larger the sample the more accurately it represents the larger population

- Top of pg26


Naturalistic Observations• Not just about

chimpanzees in nature.

Correlational Research Strategies:

Correlation• The Correlation coefficient is a statistical measure of

relationship. • Is there a relationship between stress and illness?

• Is there a relationship between test scores and school success?

• Scatter plots: pg 28


Correlation and Causation• Correlation is not causation

• For example:– Low self esteem and depression have a

positive correlation• Low self-esteem could cause depression• Depression could cause low self esteem• Distressing events or biological disposition could

cause both depression and low self esteem.


Illusory Correlation• When we believe there is a relationship between

two things, we are likely to notice and recall instances that confirm our belief.

– Full moon correlations– Getting cold and wet makes one catch a cold– Sugar makes kids hyperactive


Perceiving Order in Random Events

• Shown random data, scientists and psychics alike can often “see” an interesting pattern.

• If I flip a coin 9 times and ‘heads’ comes up each time, is it more likely that the tenth time will be ‘tails’?

• When no ones wins a given lottery draw, the prize of the subsequent draw increases and more people buy tickets. How does this affect the chances of a single ticket winning?

• Do professional athletes go on “streaks” or develop “hot hands” – pg 32

Experimental Research Strategies:

• Experiments enable a researcher to focus on the possible effects of one or more factors by:

1. Manipulating the factors of interest

2. Holding constant (“controlling”) other factors

• E.g. There is a strong positive correlation between breast feeding and later intelligence. Is the later intelligence caused by breast feeding? Pg 33


Evaluating Therapies• If we get better 3 days after taking a

certain pill we tend to think that pill is the reason we got better.

• 1700’s bloodletting seemed to be very effective.

• To find if something is actually effective we need to experiment


Evaluating Therapies• The Placebo Effect …fake pills often

work because people believe they do.• Double-blind procedure creates an

experimental condition in which people receive the treatment and a contrasting control condition without the treatment. By randomly assigning people to these conditions the two groups should otherwise be identical.


Evaluating Therapies• The independent variable: the experimental

factor that is manipulated; the variable whose effects are being studied

• The dependent variable: the variable that may change in response to manipulations of the independent variable (e.g. behaviour or mental process)

• “Experiments aim to manipulate an independent variable, measure the dependent variable, and control all other variables” –pg35

• Can Subliminal Tapes Improve Your Life? –pg 35

Statistical Reasoning:

• Bombarded by numbers

• Harper’s Index


Measures of Central Tendency• Mode – the most frequently occuring

score in distribution

• Mean – the average

• Median – the middle score in a distribution; half the scores above and half are below it.


Measures of Variation• Averages based on scores with low

variability are more reliable than averages based on scores with high variability

• Range: the difference between the highest and lowest scores in a distribution

• Standard Deviation: a computed measure of how much scores vary around the mean score


Making Inferences• When is an observed difference

reliable?1. Representative samples are better than

biased samples

2. Less-variable observations are more reliable than those that are more variable.

3. More cases are better than fewer


Making Inferences

• When is a difference significant?– Statistical significance: a statistical

statement of how likely it is that an obtained result occurred by chance.

– Occurs when the sample averages are reliable and the difference between them is relatively large.

research strategies in psychology. descriptive research strategies: the case study

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