Population

the set of all individuals of interest for a particular study

Parameter

a value that describes a population

Sample

a set of individuals from a population intended to represent the population in the research study.

Statistic

a value that describes a sample.

Greek letter Σ (sigma)

stands for “the summation of”

Nominal 

For categories that have no inherent numerical value or ranking

Ordinal

defined - categories that are assigned to rank-ordered ranging from low to high.

Interval

categories for all cases expressed in the same units.

Categorical variables

Data arranged in response categories, applies to nominal and ordinal levels.

Numerical variables

Data are represented as numbers with no attempt to categorize them applies to interval levels.

Dichotomous variables

(two categories) can be nominal or ordinal can it be rank ordered.

Discrete variables

No intermediate values can fall between adjacent categories; separate, indivisible categories

Continuous variables

Infinite number of possible values that fall between observed values