Descriptive statistics

Provides us with tools (tables, graphs, averages, ranges, correlations) for organizing and summarizing the inevitable variability in collections of actual observations or scores

Inferential Statistics

Statistics also provides tools (a variety of tests and estimates) for generalizing beyond collections of actual observations.

Population

Any complete collection of observations or potential observations

Sample

Any smaller collection of actual observations from a population.

Random Sampling

A procedure designed to ensure that each potential observation in the population has an equal chance of being selected in a survey.

Random Assignment

A procedure designed to ensure that each person has an equal chance of being assigned to any group in an experiment.

Data

A collection of actual observations or scores in a survey or an experiment

Qualitative Data

A set of observations where any single observation is a word, letter, or numerical code that represents a class or category.

Ranked Data

A set of observations where any single observation is a number that indicates relative standing.

Quantitative Data

A set of observations where any single observation is a number that represents an amount or a count.

Level of Measurement

Specifies the extent to which a number (or word or letter) actually represents some attribute and, therefore, has implications for the appropriateness of various arithmetic operations and statistical procedures.

Nominal Measurement

Words, letters, or numerical codes of qualitative data that reflect differences in kind based on classification.

Ordinal Measurement

Relative standing of ranked data that reflects differences in degree based on order.

Interval/Ratio Measurement

Amounts or counts of quantitative data reflect differences in degree based on equal intervals and a true zero.

graph TD
    A[Data] -->G(Words)
    G --> B[Qualitative]
    B -.-> |Yes,No| B[Qualitative]
    B -->|Classification| D[Nominal]
    A --> C(Numbers)
    C -->|Relative| E[Ranks]
    E -.->|1st 2nd...| E[Ranks]
    E -->|Ordiner| H[Ordinal]
    C -->|Amount/Count| F[Quantitative]
    F -.->|100kg, 120kg...| F[Quantitative]
    F -->|Equal intervals/ True Zero| I[Interval/Ratio]