Quantification

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Garrett Tancredy Fraley Born Jan 31, 2003, 1121
p.m.
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Part II Measuring Psychological Variables

• In the last section, we discussed reasons why
  scientific approaches to understanding psychology
  may be useful
• A key concept was systematic observation

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Systematic Observation

• In order to systematically observe something, it
  is critical to have a well-defined or
  quantitative system of measurement.
• Simple example How far is projector screen from
  the podium?

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A More Complex Example

• What about something like How shy is Fraley?
• This seems a bit more tricky because shyness,
  unlike distance, isnt something that were used
  to measuring with an everyday tool. It is a bit
  more abstract and elusive.

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Can Psychological Properties be Measured?

• However, there are two points worth considering.
• There is nothing intrinsically concrete about
  inches, feet, miles, and meters. These are
  standard (i.e., conventional and agreed upon),
  but ultimately arbitrary, metrics.
• Distance isnt exactly a thing in the way that
  a stool is a thing. Distance, however, is an
  extremely useful abstraction. Is there any
  reason why shyness should be any more intractable
  abstraction than distance?

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Can Psychological Properties be Measured?

• A common complaint Psychological variables
  cant be measured.
• We regularly make judgments about who is shy and
  who isnt who is attractive and who isnt who
  is smart and who is not

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Quantitative

• Implicit in these statements is the notion that
  some people are more shy, for example, than
  others
• This kind of statement is inherently
  quantitative.
• Quantitative It is subject to numerical
  qualification.
• If it can be numerically qualified, it can be
  measured.

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Interim Summary

• Shyness, like distance, is a useful abstraction
• We use the concept of shyness, like distance, in
  quantitative ways (e.g., greater than, less than)
• One goal of psychological measurement is to find
  standard and useful ways to systematically
  measure psychological constructs

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Quantification

• An important first-step in measurement is
  determining whether a variable is categorical or
  continuous.
• Why? This determines how we quantify or measure
  the variable.
• Variable A feature for which people differ.
• Shyness some people are more shy than others
• Age some people are older than others

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Nominal Scale

• With categorical, qualitative, or nominal
  variables people either belong to a group or not
• Examples
• country of origin
• biological sex (male or female)
• animal or non-animal
• married vs. single
• Quantitative question How many people belong to
  each category?

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Scales of Measurement Nominal Scale

• Sometimes numbers are used to designate category
  membership
• Example
• Country of Origin
• 1 United States 3 Canada
• 2 Mexico 4 Other
• However, in this case, it is important to keep in
  mind that the numbers do not have intrinsic
  meaning

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Continuous Variables

• With continuous variables, people vary in a
  graded way with respect to the variable
• Examples
• age
• intelligence
• shyness
• Quantitative question How much or to what
  degree

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Scales of Measurement Continuous Variables

• When we assign numbers to people (i.e., when we
  scale people) with respect to a continuous
  variable, those numbers represent something that
  is more tangible than those used in a nominal
  system.
• Exactly what the numbers mean, and how they
  should be treated, however, depends on what kind
  of continuous metric were dealing with . . .

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Scales of Measurement Ordinal

• Ordinal Designates an ordering quasi-ranking
• Does not assume that the intervals between
  numbers are equal
• Example
• finishing place in a race (first place, second
  place)

1st place
2nd place
3rd place
4th place
1 hour 2 hours 3 hours 4 hours 5 hours 6 hours 7
hours 8 hours
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Scales of Measurement Interval

• Interval designates an equal-interval ordering
• The distance between, for example, a 1 and a 2 is
  the same as the distance between a 4 and a 5
• Example Common IQ tests
• the difference between someone with a score is
  120 and someone with a score of 100 is the same
  as the difference between people with scores of
  80 and 60 (i.e., 20 points)

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Scales of Measurement Ratio

• Designates an equal-interval ordering with a true
  zero point (i.e., the zero implies an absence of
  the thing being measured)
• Example
• the number of intimate relationships a person has
  had
• 0 quite literally means none
• a person who has had 4 relationships has had
  twice as many as someone who has had 2

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Scales of Measurement Additional Comments

• In general, most observable behaviors can be
  measured on a ratio-scale
• In general, many unobservable psychological
  qualities (e.g., extraversion), are measured on
  interval scales
• We will mostly concern ourselves with the simple
  categorical (nominal) versus continuous
  distinction (ordinal, interval, ratio)

variables
categorical
continuous
ordinal
interval
ratio