It is a measurement which may, sometimes, be called an extreme observation or an outlier. However, there is no agreed definition for outliers.
Outliers.
It is one of the informal definitions for an outlier.
outliers
Usually they would be observations with very low probabilities of occurrence.
I believe outliers is the best answer to this question. The previous answer was average, which is the mean.
You may be referring to the statistical term 'outlier(s)'. Also, there is a rule in statistics called the '68-95-99 Rule'. It states that in a normally distributed dataset approximately 68% of the observations will be within plus/minus one standard deviation of the mean, 95% within plus/minus two standard deviations, and 99% within plus/minus three standard deviations. So if your data follow the classic bell-shaped curve, roughly 1% of the measures should fall beyond three standard deviations of the mean.
They are observations with a low likelihood of occurrence. They may be called outliers but there is no agreed definition for outliers.
Outliers
Extreme values. They might also be called outliers but there is no agreed definition for the term "outlier".
The answer depends on what the standard deviation is.
variances
This is 3 standard deviations above and below the mean.