Variables and their Operational Variables and their Operational DefinitionsDefinitions

Measuring Variables

Introduction

The basic requirements of all research in psychology is that a researcher must be able

to measure the variables of interest.

1.Objective versus subjective measures

2.Structured versus unstructured measures

3.Types of Variables

4.Scales of Measurements

5.Reliability

6.Validity

7.Operational Definition

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

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

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

Types of Variables

Variables

Discrete/Categorical Continuous

Ordinal

Interval

Ratio

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., 1.2345, 2.23, 5.2458

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

Scales of MeasurementOrdinal 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

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

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 120 pounds

• amount of time to complete a task

Types of MeasurementSelf-report (behavioral, cognitive, affective)• usually questionnaires or interviews the

measure how people report that they act, think or feelTest (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

Variables and their Operational Variables and their Operational DefinitionsDefinitions

Operational Definition

Operational Definitions

An operational definition specifies the observable

and measurable characteristics of a term

or concept.

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.

A researcher could define depression in terms of…

1. Behavioral observations (e.g., affect level, content analysis of speech patterns)

2. Survey (e.g., Beck Depression Inventory)

3. Physiological measures (e.g., lateralization of EEG brain wave activity)

Operational Definitions

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.

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.

As researchers, we have to accept that there is no perfect operational definition for a given

construct (e.g., IQ).