statistics

Statistic

A measurable quantity calculated from a sample.

Summary statistic

A statistic used to describe data (e.g., mean, median, mode).

Categorical data

Data grouped into categories (e.g., yes/no, genotype).

Ordinal data

Categorical data with a natural order (e.g., Likert scales).

Quantitative data

Numerical data (discrete or continuous).

Discrete data

Whole‑number values (e.g., colony counts).

Continuous data

Values within a range (e.g., height, concentration).

Mean

Arithmetic average of a dataset.

Median

Middle value when data are ranked.

Mode

Most frequent value.

Range

Difference between maximum and minimum values.

Quartiles

Values dividing data into four equal parts.

Interquartile range

Upper quartile minus lower quartile.

Standard deviation

Average distance of values from the mean.

Contingency table

Table showing frequencies of categorical variables.

Histogram

Graph showing distribution of quantitative data.

Box plot

Graph showing median, quartiles, and range.

Purpose of statistics

To summarise data and test hypotheses.