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Section 8.8 Glossary

population mean
The true mean of a quantity in an entire population, as opposed to the sample mean, which is calculated from a subset.
parameter
One of the values that specify a particular distribution in a set of distributions -- for example, the parameters of a normal distribution are the mean and standard deviation.
estimator
A statistic calculated from a sample that is used to estimate a parameter of the population.
consistent
An estimator is consistent if it converges to the actual value of a parameter as the sample size increases.
unbiased
An estimator is unbiased if, for a particular sample size, the average of the sample estimates is the actual value of the parameter.
mean squared error (MSE)
A measure of the accuracy of an estimator -- it’s the average squared difference between estimated and true parameter values, assuming the true value is known.
robust
An estimator is robust if it remains accurate even when a dataset contains outliers or errors -- or does not perfectly follow a theoretical distribution.
resampling
A way to approximate the sampling distribution of an estimate by simulating the sampling process.
parametric resampling
A kind of resampling that estimates population parameters from sample data and then uses a theoretical distribution to simulate the sampling process.
sampling distribution
The distribution of a statistic across possible samples from the same population.
standard error
The standard deviation of a sampling distribution, which quantifies the variability of an estimate due to random sampling (but not measurement error or non-representative sampling).
confidence interval
An interval that contains the most likely values in a sampling distribution.
sampling bias
A flaw in the way a sample is collected that makes it unrepresentative of the population.
measurement error
Inaccuracy in how data are observed, measured, or recorded.