THE READING ROOM
Mean, median and range answer different questions
A lifespan headline may use average without saying how the number was calculated. Before comparing it with another headline, check whether the source reports an arithmetic mean, a median survival estimate or something else. Similar words do not guarantee comparable measurements.
Editorial team / by PawLine. Source-checked November 13, 2026. Not independently veterinary-reviewed.
The arithmetic mean shares out the total
For a complete list of lifetimes, adding all values and dividing by the number of records gives the arithmetic mean. In our first invented set, nine values add to 108 years, so the mean is 12 years. This is a mathematical example, not a new estimate of dog longevity or a reanalysis of a published dataset.
Teng et al.: Life tables for UK companion dogs ↗Evidence for this context, not a review or endorsement of Longview.
The median locates the middle
For nine complete values in order, the fifth value is the median. The board keeps that value at 12 while changing the other records. In the published 2024 study, median survival came from a survival curve that also incorporated incomplete follow-up. Sorting nine complete values illustrates the idea of a middle, not the full research method.
McMillan et al.: Longevity of companion dog breeds ↗Evidence for this context, not a review or endorsement of Longview.
The range shows the observed endpoints
Our invented wide set runs from 6 to 18 years. Its narrow set runs from 10 to 14. Both have a mean and median of 12. A range is only the minimum and maximum in that set. It is not a guarantee that future observations will stay inside those endpoints.
McMillan et al.: Longevity of companion dog breeds ↗Evidence for this context, not a review or endorsement of Longview.
A confidence interval is something else
A confidence interval expresses uncertainty around an estimated quantity under the analysis. It is not the age band containing 95 percent of individual dogs. When a paper reports an interval beside its median, do not turn the endpoints into a personal lifespan window. Read the label and method together.
McMillan et al.: Longevity of companion dog breeds ↗Evidence for this context, not a review or endorsement of Longview.