Descriptive Statistics 1 - Scales of Measurement and Central Tendency (Weeks 1-2)

Vocabulary flashcards covering scales of measurement, variable types, and central tendency concepts from Weeks 1-2 notes.

Nominal scale

A data scale where categories are labels with no intrinsic order; observations belong to mutually exclusive categories (e.g., biological sex).

Ordinal scale

A data scale with a meaningful order or ranking, but the gaps between ranks are not necessarily equal.

Interval scale

A data scale with ordered categories and equal intervals between values, but with no true zero (e.g., temperature in Celsius or Fahrenheit).

Ratio scale

A data scale with ordered categories, equal intervals, and a true zero representing absence of the quantity (e.g., distance, weight).

Mutually exclusive

Categories are non-overlapping; an observation fits into one and only one category.

Practical distinction

A workable separation where an item mainly belongs to one category but could fit a little in another.

Absolute zero

The zero point on a ratio scale indicating none of the quantity.

True zero

Another term related to absolute zero; only ratio scales have a true zero point.

Identity (scale principle)

Nominal values serve as labels to identify categories without implying order or quantity.

Order (scale principle)

The ability to rank observations; associated with ordinal scales (and higher).

Quantity (in measurement scales)

Information about magnitude provided by scales; interval and ratio scales convey quantity through equal intervals.

Biological sex (example)

An example of nominal data.

Class rank (example)

An example of ordinal data.

Temperature (example)

An example of interval data (e.g., Celsius or Fahrenheit).

Distance (example)

An example of ratio data.

Mean (X-bar)

The arithmetic average; computed as the sum of scores divided by the number of scores (N). Notation: X̄.

Median

The middle value in an ordered data set; for even N, the average of the two middle values.

Mode

The most frequent value in a data set; a data set can be unimodal or multimodal.

Skew (positive/negative)

Asymmetry of a distribution; positive skew has a longer right tail, negative skew a longer left tail.

Outlier

An observation far from the rest of the data; can heavily affect the mean.

Descriptive statistics

Statistics that summarize or describe features of a data set (e.g., mean, median, mode, frequency) without generalizing to a population.

Inferential statistics

Statistics that draw conclusions or inferences about a population from a sample (hypothesis testing, estimation).

Independent variable (IV)

The predictor variable; the variable used to explain or predict the dependent variable.

Dependent variable (DV)

The outcome variable; the variable that is explained or predicted.

Predictor

Another term for the independent variable (IV) used to explain DV.

Continuous variable

A variable that can take an infinite number of values within a given range (e.g., height, time).

Discrete variable

A variable with a finite or countable number of values (e.g., number of students).

Bimodal

A distribution that has two modes (two values or ranges that occur most frequently).

Chi-square test of independence

A statistical test used to determine if there is an association between two categorical variables.