Parameter
Parameter is a fixed numerical property of an entire population, such as the true mean or a regression slope. Researchers rarely observe the whole population, so parameters are estimated from sample data using rules called estimators.
Also known aspopulation parameter
See it move
The infographic is a two-column comparison distinguishing a population parameter from a sample estimate. The left column, 'Parameter', describes a fixed population truth — such as μ, σ², or β — that is usually unknown and never changes from sample to sample. The right column, 'Estimate', describes a sample-based approximation — such as x̄, s², or b — that is computed from data and changes each time a new sample is drawn; the note cautions that estimates should always be reported with their standard errors.
Check yourself
A researcher surveys 300 randomly selected European university students and calculates an average weekly study time of 22.4 hours. She wants to draw conclusions about all European university students. In this context, which of the following is a parameter?