Mean
Definition
The arithmetic average of a dataset, calculated as the sum of all values divided by the number of values. Sensitive to extreme values (outliers), which can pull it away from the bulk of the data.
- Formula
- Sum of values divided by count of values
- Sensitivity
- Skewed by outliers
- Also called
- Arithmetic average
- Common pairing
- Reported alongside standard deviation
Common questions
When should the median be reported instead of the mean?+
When a dataset has extreme values or a skewed shape, such as a handful of very large fraud losses or unusually long time-to-close cases, the mean is pulled toward those outliers and the median gives a more representative central value.
Why does the mean matter in forensic measurement work?+
Repeated measurements of the same item, such as replicate instrument readings, are typically summarised as a mean with an associated uncertainty, so the mean becomes the reported value a court sees rather than any single raw reading.
Related terms
- Median
- The middle value of a dataset sorted in ascending or descending order. For an even number of values, it is the average...
- Mode
- The value that appears most frequently in a dataset. Most informative for discrete or categorical data; for continuous measurement data it is...
- Refractive Index (RI)
- A physical property of glass measuring how much light bends as it passes through. RI is the primary discriminating characteristic used in...
- Standard Deviation
- The square root of the variance. Expressed in the same units as the original measurement, making it interpretable as a typical distance...
- Variance
- The average of the squared deviations from the mean. Because it squares the original unit of measurement, variance is not directly interpretable...