Statistics Dictionary
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Confidence Interval
Statisticians use a confidence interval to express the degree of
uncertainty associated with a sample
statistic.
A confidence interval is an
interval estimate
combined with a probability statement.
For example, suppose a statistician conducted a survey and computed an interval
estimate, based on survey data. The statistician might use a
confidence level
to describe uncertainty associated with the interval estimate.
He/she might describe the interval estimate as a "95% confidence interval".
This means that if we used the same sampling method to select different samples and
computed an interval estimate for each sample,
we would expect the true population parameter to fall within the interval estimates
95% of the time.
Confidence intervals are preferred to
point estimates
and to interval estimates, because only confidence
intervals indicate (a) the precision of the estimate and (b) the uncertainty of
the estimate.