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A confidence region is similar to a confidence interval, but is calculated for two or more variables at the same time; for example, the difference in cost and the difference in the effectiveness of two treatments in a cost effectiveness analysis.
If a set of measurements, such as the variables used to estimate an incremental cost-effectiveness ratio, were repeated many times and a confidence region calculated in the same way for each set of measurements, then a certain percentage of the time (typically 95%), on average, the confidence region would include the point representing the actual values of the cost and the effectiveness.
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