Part ii measuring psychological variables
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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. Systematic Observation.

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Part ii measuring psychological variables
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
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?

A more complex example
A More Complex Example

  • What about something like “How shy is Dr. Powell?”

  • 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
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 abstraction than distance?

Can psychological properties be measured1
Can Psychological Properties be Measured?

  • 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 is not.


  • 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.

Interim summary
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


  • 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
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
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

Continuous variables
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
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 we’re dealing with . . .

Scales of measurement ordinal
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

Scales of measurement interval
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)

Scales of measurement ratio
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
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)