Such as stratified samples, an outlier is an observations that is numerically distant from the rest of the data.
Statistics derived from data stes that include outliers will ofthen be misleading.
For example, in calculating the average temperature of 10 objects in a room, if most are between 50 and 55°F, but there is an oven a 300°F, the median of the data can be 53, but the average temperature will be 135°F.
In this case, the median refelects the temperature of the random smaple of an object better tahn the mean. Outliers may be indicative of data belonging to a different population from the rest of the established samples.