1. Variables and their Operational Definitions
Measuring Variables

2. Introduction
The basic requirements of all research in psychology is that a researcher must be able to measure the variables of interest.
Objective versus subjective measures
Structured versus unstructured measures
Types of Variables
Scales of Measurements
Reliability
Validity
Operational Definition

3. Objective Versus Subjective
It is traditional in psychology to differentiate between objective and subjective measures.
The distinction is essentially between observations that all observers will agree about (objective measures) and those observations which are idiosyncratic to a particular observer and which are not shared by all observers (subjective measures)
Example: Objective
speed of reaction time to a signal
the number of words correctly recalled
Example: Subjective
psychologists’ assessments of dangerousness of a sex offender

4. Structured versus Unstructured
Research methods in psychology vary greatly in the degree of structuring involved.
Structured
highly structured methods are employed when there is a degree of clarity about the nature of the variables being measured and the likely range of different answers
Unstructured
unstructured methods are employed more when the psychologist is exploring issues that have not been widely researched before

5. Types of Variables
The foundation of experiments are independent and dependent variables
Independent Variables
the condition that the researcher controls (manipulates) in order to test the variable’s effect on some outcome (dependent variable)
Dependent Variables
outcome variables of your research
it is what the researcher is measuring or observing

6. Discrete/Categorical
Types of Variables
Variables
Discrete/Categorical
Continuous
Ordinal
Interval
Ratio

7. Dichotomous Variables
Types of Variables
Dichotomous Variables
variables that have only 2 categories
e.g., yes or no
Discrete Variables
variables that increases and decreases by whole units
e.g., 1, 2, 3
Continuous Variables
variables that theoretically assume infinite number of values
e.g., , 2.23,

8. Scales of Measurement Nominal Scale
categorical; simple classification; identity; data consist of frequencies only
a scale of measurement in which events are assigned to categories
naming scales
they represent categories where there is no basis ordering categories
Examples
eye color
gender
race

9. Scales of Measurement Ordinal Scale
categories that can be ordered along a pre-established dimension
but, no way of knowing how different the categories are from one another
there are not equal intervals between the items
arrangement of height (tall, normal short); winners in race (1st, 2nd, 3rd)
Examples
height: tall, medium, short
winners: 1st, 2nd , 3rd

10. Scales of Measurement Interval Scale
rank order with equal intervals; identity, magnitude & equal unit size
permits rank ordering of events with the assumption of equal intervals between adjacent events
Examples
temperature: Fahrenheit & Celsius
SAT tests: impossible to get zero
IQ: impossible to have zero IQ

11. Scales of Measurement Ratio Scale
rank order; equal interval; presence of a true zero point; identity, magnitude, equal unit size, absolute zero
can make ratio comparisons “twice as much” or “3 times bigger”
Examples
height: 165 cm 5’6”
weight: 65 kg pounds
amount of time to complete a task

12. Types of Measurement Self-report (behavioral, cognitive, affective)
usually questionnaires or interviews the measure how people report that they act, think or feel
Test (ability tests, personality)
a measure instrument used to assess individual differences in various content areas
Behavioral measures (counting behaviors, classifying behaviors)
measures taken by carefully observing and recording behavior
Physical measures (weight, pulse, blood measure, heart rate)
measures of bodily activity

13. Variables and their Operational Definitions

14. Operational Definitions
In order to conduct research and communicate meaningful with others, researchers must define the terms and concepts explicitly.
For example, depression is defined conceptually as a state of being in which the individual exhibits initiative and has sad and gloomy thoughts.
An operational definition specifies the observable and measurable characteristics of a term or concept.
A researcher could define depression in terms of…
Behavioral observations (e.g., affect level, content analysis of speech patterns)
Survey (e.g., Beck Depression Inventory)
Physiological measures (e.g., lateralization of EEG brain wave activity)

15. Operational Definitions
An operational definition is a detailed specification of how one would go about measuring a given variable.
Operational definitions should be tied to the theoretical constructs under study. The theory behind the research often claries the nature of the variables involved.
Operational definition can range from very simple and straightforward to quite complex depending on the nature of the variable and the needs of the researcher.
As researchers, we have to accept that there is no perfect operational definition for a given construct (e.g., IQ).