Introduction to Statistics - Categorical Data and Variables

Vocabulary flashcards covering core statistical terminology, data types, and categorical data summarization methods from lecture notes.

Variable

A characteristic that can differ from one observational unit to the next.

Explanatory Variable

A variable in a statistical study that is examined to determine whether it explains or causes changes in a response variable.

Response Variable

A variable in a statistical study that measures an outcome or result.

Parameter

A numerical summary or characteristic that describes an entire population.

Statistic

A numerical summary or characteristic computed from a sample of data.

Population Data

Data collected from every member or unit in the defined population.

Sample Data

Data collected from a subset or sample of units selected from the target population.

Summarizing Categorical Variables

A two-step procedure that involves counting how many observations fall into each category and calculating the percentage in each category.

Visual Summaries of Categorical Variables

Graphical methods used to represent categorical data, specifically pie charts, bar charts, and clustered bar charts.

Bar Graph

A chart where categories are listed on the x-axis and the height of each bar corresponds to frequency or count, relative frequency, or percentage.

Misleading Graph Example

A graphical display, such as the CNN Poll of Polls line chart showing approval and disapproval ratings over time, used to demonstrate how visual presentations can obscure or distort statistical trends.

Table 2.1 Seatbelt Use by Twelfth-Graders When Driving

A categorical frequency and percentage distribution table summarizing seatbelt usage among $3042$ twelfth-graders (Always: $55.4\%$, Most times: $19.0\%$, Sometimes: $13.6\%$, Rarely: $8.2\%$, Never: $3.8\%$).