“If a thing exists, it exists in some amount; and if it exists in some amount, it can be measured....
Sponsored Links
This presentation is the property of its rightful owner.
1 / 19

“If a thing exists, it exists in some amount; and if it exists in some amount, it can be measured.” –E. L. Thorndike (1914) PowerPoint PPT Presentation


  • 81 Views
  • Uploaded on
  • Presentation posted in: General

“If a thing exists, it exists in some amount; and if it exists in some amount, it can be measured.” –E. L. Thorndike (1914). “If you haven't measured it you don't know what you are talking about.” -Lord Kelvin. Today’s Questions. What does it mean to measure a psychological variable?

Download Presentation

“If a thing exists, it exists in some amount; and if it exists in some amount, it can be measured.” –E. L. Thorndike (1914)

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


“If a thing exists, it exists in some amount; and if it exists in some amount, it can be measured.”

–E. L. Thorndike (1914)


“If you haven't measured it you don't know what you are talking about.”

-Lord Kelvin


Today’s Questions

  • What does it mean to measure a psychological variable?

  • What is the difference between categorical and continuous variables, and why does the difference matter?


Basic Terminology

  • Variable: a characteristic that can vary or take on different values

    • Example: height is a variable

  • Value: a number representing one of many possible “states” of the variable

    • Example: some possible values of height are 6 feet or 4 feet 2 inches

  • Score: a specific value for a given person

    • Example: my score on the variable of height is 6 feet


Systematic Observation

  • In order to systematically observe something, it is critical to have a well-defined or quantitative system of measurement.

  • Simple example: How tall is Josh?


A More Complex Example

  • What about a question such as “How shy is Josh?”

  • This seems a bit more tricky because shyness, unlike height, 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.

    • Height isn’t exactly a “thing” in the way that a desk is a thing. Height, however, is an extremely useful abstraction. Is there any reason why shyness should be any more intractable than height?

    • There is nothing intrinsically concrete about inches, feet, miles, and meters. These are standard (i.e., conventional and agreed upon), but ultimately arbitrary, metrics.


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 suffering and who isn’t; which marriages are functioning well and which are not


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: subject to numeric qualification.


Interim Summary

  • Shyness, like distance, is a useful abstraction

  • We use the concept of shyness, like height, 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 property of a variable determines how we quantify the variable, how we model its statistical behavior, and the way we analyze data regarding that variable.


Nominal Scale

  • With categorical, taxonic, qualitative, or nominal variables, people either belong to a group or they do 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 States3 = Canada

    2 = Mexico4 = Other

  • However, in this case, it is important to keep in mind that the numbers do not have numeric implications; they are simply convenient labels


Continuous Variables

  • With continuous variables, people vary in a graded way with respect to the property of interest

  • Examples:

    • age

    • working memory capacity

    • marital discord

  • Quantitative question: How much? or To what extent or 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 meaningful than those used with nominal variables

  • Exactly what those numbers mean, and how they should be treated, however depends on the exact metric of the continuous variable...


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 hour2 hours3 hours4 hours5 hours6 hours7 hours8 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 are assumed to use an interval metric


Scales of Measurement: Ratio

  • Ratio: designates an equal-interval ordering with a true zero point (i.e., the zero implies an absence of the thing being measured)

  • Example:

    • 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


  • Login