Types of Variables

Variable

something that varies or changes

• At least two levels or possible values (but possibly more)

Constant

something that does not vary

• Sometimes constants could be variables, but are held constant in the study in question

• One level or possible value

Qualitative

non-numeric

• Categories could be assigned numbers, but those numbers aren’t meaningful

• Ex. 1 = “neuroscience major”, 2 = “psychology major”, 3 = “education major”, etc.

Discrete variables

are count variables that involve integers

• Cannot be a decimal or fraction

• Limited number of possible values

Ex: Number of children a family has

Continuous variables

involve nonintegers

• Between any two values, there may be an infinite number of others

Ex: Time it takes someone to finish a race

• Interval variables:

• Are distributed in equal units (equidistant scale), BUT

• Scale has no true zero

Ratio variables:

• Are distributed in equal units (equidistant scale), AND

• Scale has a true zero

• Independent variable

manipulated

• In an experiment, the number of levels of an independent variable is the number of experimental conditions

Quasi-independent variable

cannot be (reasonably) manipulated

• Personal attributes or traits

• Can be treated as an IV and affect DV

Dependent variable (DV)

measured

• Outcome or response