Exact Intervals and Tests for Mean of Symmetrical Population When One 'Sample' Value Possibly an Outlier.

The continuous data are n observations that are believed to be a random sample from a symmetrical population. Confidence intervals and significance tests for the population mean are desired. There is, however, the possibility that either the smallest observation or the largest observation is an outlier. That is, the population providing this observation differs from the symmetrical population providing the other n - 1 observations. If this occurs, intervals and tests are desired for the mean of the population providing the other n - 1 observations. Some investigation difficulties can be overcome if intervals and tests can be developed that are simultaneously usable for all of these three situations a confidence coefficient, or significance level, has the same value for all three situations. Two kinds of intervals and tests with this property are developed. These results always involve both the next to largest and next to smallest observations and should have at least moderately high efficiencies. Also, some extensions are considered, such as allowing each observation to be from a different population. Author