Descriptive Statistics

A population is the entire group of interest; a sample is a subset of the population that is actually observed and used to draw conclusions.

A parameter is a numerical summary of a population; a statistic is a numerical summary computed from a sample.

Qualitative (categorical) data describe categories or labels; quantitative (numerical) data are measured or counted numbers.

Discrete data take countable, separate values (often integers); continuous data can take any value within an interval (measurements).

Nominal, ordinal, interval, and ratio.

The ratio level has a true (meaningful) zero, so ratios of values are meaningful; the interval level has no true zero.