# Stats: Estimation

## Definitions

Confidence Interval
An interval estimate with a specific level of confidence
Confidence Level
The percent of the time the true mean will lie in the interval estimate given.
Consistent Estimator
An estimator which gets closer to the value of the parameter as the sample size increases.
Degrees of Freedom
The number of data values which are allowed to vary once a statistic has been determined.
Estimator
A sample statistic which is used to estimate a population parameter. It must be unbiased, consistent, and relatively efficient.
Interval Estimate
A range of values used to estimate a parameter.
Maximum Error of the Estimate
The maximum difference between the point estimate and the actual parameter. The Maximum Error of the Estimate is 0.5 the width of the confidence interval for means and proportions.
Point Estimate
A single value used to estimate a parameter.
Relatively Efficient Estimator
The estimator for a parameter with the smallest variance.
T distribution
A distribution used when the population variance is unknown.
Unbiased Estimator
An estimator whose expected value is the mean of the parameter being estimated.