# Variables, etc

Variables

• Defining, Measuring, & Manipulating

• IVs

• DVs

• Levels?

• Confounding variables

• Reliability

• Validity

Operational definition of a variable

• A definition of a variable in terms of operations/activities that a research uses to measure/manipulate it

• Gives a variable a concrete definition so you can actually use it in an experiment, this allows the researcher to maintain consistency.

• All variables involved in a study should be operationalized

• Dependent Variables (what is measured)

• Independent Variables (what is manipulated)

Levels of Measurement

• Identity

• Measurement in which different objects receive different scores

• Magnitude / ordinality

• Measurement in which the ordering of numbers reflects the ordering of variables

• Equal Unit Size

• A difference of 1 is the same amount throughout the entire scale

• EX “the height difference between two people who are 64 inches tall and 65 inches tall is the same difference between those who are 72 inches tall and 73 inches tall”

• Absolute Zero

• Assigning a score of zero indicates an absence of the variable being measured

Scales of Measurement

• Nominal

• Ordinal

• Interval

• Ratio

Discrete Variables

Continuous Variables

Types of Measures

• Self-report

• Tests

• Behavioral

• Physical

Reliability

• Types of Reliability

• test/retest

• Alternate-forms

• Split-half

• Interrater

• How to Measure Reliability

Validity

• Content

• Criterion

• Construct