Round up - Qual and Quant
• Why have two types of research
methodologies?
• Don’t replace each other
• we will always need statistics
• Each has its own place
• make sure you use the right type in the right
circumstances
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Why use quant?
• causes/relationships = PREDICITON
• can predict changes, etc (clinical, legal,
aviation, etc etc etc)
• Generalization to the population is
important
• will my cure for AIDS for for everyone?
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Why use qual?
• Aim: to know what something “is like”
• feminists, educationalists, activists
• Can express things empathically
• The findings are not generalizable
• silly to talk about the average of “what its like”
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Using qual when you shouldn’t
• Gee, measuring this variable is too hard, so
I’ll just get a “feel” for the relationship by
asking people what it was like
• tells you nothing - numbers are at the heart of
prediction
• no numbers, no generalization
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Using quant when you shouldn’t
• I think the media is racist. I will count the
number of racist words used in newspaper
and TV to prove all the media is racist
• Predicting doesn’t apply to everything
• Sometimes you can’t generalize
• not all newspapers are racist
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Who is going to read it?
• Both types require special knowledge to
interpret
• Qual research seems understandable by
anyone
• Remember the “Racism in the media” scandal?
• Know the limits of the research types.
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Psychometrics
• Aim: measure aspects of the psychology of
a single person
• don’t care about populations - just old Bob by
himself
• Why measure only a single person?
• Employment selection
• Diagnosis
• Evaluation
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A brief history of psychometrics
• Idea of testing people for selection
• ideas of “tests from the gods” in mythology
• ancient Chinese (2200 BC)
• “Scientification” occurred in the late 1800s
• Galton and Cattell (RT)
• Binet & Simon: intelligence testing in
France (schools)
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In come the Americans
• Goddard: Detection of “feebleminded”
immigrants at Ellis Island (1910)
• Army tests (officer selection) - Yerkes 1916
• Alpha test (verbal test)
• Beta test (non verbal)
• After the war: aptitude testing (for any job!)
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The basic idea of testing
• We can’t measure psychological variables
directly - They don’t exist!
• Psychometrics introduces the idea of a
behaviour domain
• We can think of many things related to any
psychological phenomenon
• All of these things together are the behaviour
domain
• What is the behaviour domain of intelligence?
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Behaviour domains
• The things in the domain are very specific
• The list of a behaviour domain can be very
long - infinately long, maybe?
• We want to know that a person displays
most of these behaviours - but we can’t!
• Similar to the problem of research with
populations and samples!
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Sampling the behaviour domain
• In research, to talk about populations we
talked about samples (and could generalize)
• Psychometrics does the same - we want to
talk about the entire behaviour domain, but
we will use only a sample of these
behaviours
• Each “question” in a test is a “subject”
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Sampling the domain: Example
• We begin by thinking of as many members
of the behaviour domain as possible
• Randomly select a few of them
• That is the test!
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Research and psychometrics
• This similarity (overlap) is useful
• we can use our methodology knowledge to help
make better tests
• We can talk about “reliability” and “validity” of
tests to ensure we are making good tests.
• Reliability: is the test measuring accurately?
• Validity: is the test measuring only what it
claims to measure?
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