Transcript Part II: Measuring Psychological Variables • In the last section, we discussed reasons why scientific approaches to understanding psychology may be useful • A key.

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
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 the stool from the
podium?
A More Complex Example
• What about something like “How shy is Mike?”
• This seems a bit more tricky because shyness,
unlike distance, isn’t something that we’re used to
measuring with an everyday tool. It is a bit more
abstract and elusive.
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 isn’t 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 than distance?
Can Psychological Properties be
Measured?
• Finally, we must address a common complaint:
Psychological variables can’t be measured.
• We regularly make judgments about who is shy
and who isn’t; who is attractive and who isn’t;
who is smart and who isn’t
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 numerically
qualification.
• If it can be numerically qualified, then it can be
measured.
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, such as shyness
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
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?
Scales of Measurement: Nominal Scale
• Sometimes numbers are used to designate
category membership
• Example:
Country of Origin
1 = United States
2 = Mexico
3 = Canada
4 = Other
• However, in this case, it is important to keep in
mind that the numbers do not have intrinsic
meaning
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
Scales of Measurement: Continuous
Variables
• When we assign numbers to people (i.e., “scale”
people) with respect to a continuous variable,
those numbers represent something that is more
tangible
• Exactly what those numbers mean, and how they
should be treated, however depends on what kind
of continuous metric we’re dealing with . . .
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
1 hour
2 hours
2nd place 3rd place
3 hours
4 hours
4th place
5 hours
6 hours
7 hours
8 hours
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
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
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