Graphical Methods for Describing Data Distributions

The science of collecting and anayzing numerical data in large quantities for the purpose of making inferences about those from the representative sample

Population

complete set of groups of individuals or items with a common characteristic

Sample

smaller group selected from the population

Variable

any characteristic whose value may change from one individual to another

(political affiliations, number of textbook purchases, distance to school, etc)

Categorical/Qualitative Data

a collection of data divided into categories or groups

Types of Categorical/Qualitative Data

nominal & ordinal

Nominal

name, hair color, eye color, etc

Ordinal

likert scale, customer satisfaction survey data, graduation survey, etc

Types of Numerical/Quantitative Data

interval, ratio, discrete, and continous

Interval

measured along a scale, in which each point is placed at an equal distance (interval) from one another

has no true zero

**example**: temperature

Ratio

measures variable on a continuous scale with an equal distance between adjacent values

has true zero

**examples**: salary, height, weight, temperature (only Kelvin)

Discrete

values correspond to isolated points on the number line

**example**: number of students

Continous

values form an entire interval on the number line

**example:** weight