Hazy, there is lot on these definitions on the web at different technical levels in statistics. https://www.fightaging.org/ provides resources specifically for aging research (1). Many sites on gerontology and caloric restriction (CR) do the same. FighAging.org quotes the Ben Best’s site, a known researcher in the area, who explains the difference between maximum lifespan and mean lifespan. “When discussing aging it is important to distinguish two points on survival curves. Mean lifespan (average lifespan) corresponds to the age at which the horizontal line for 50% survival intersects the survival curve. Maximum lifespan corresponds to the age at which the survival curves touch the age-axis (0% survival) — and this represents the age at which the oldest known member of the species has died. (In animal studies, maximum lifespan is typically taken to be the mean lifespan of the most long-lived 10%.)” (2). Mean (or average) is not to be confused with median, the latter usually being the middle number in an ordered sequence and is better than mean when the distribution is skewed (think about the example of average income which can be much skewed by rich people while for the rest or mortals it is maybe better to using the median). You also find life expectancy, which I think is the mean number of future years to live in a survival prospect. In any case Geroprotectors.org is curated and based on PubMed searches for “…keywords relevant to pharmacological interventions in aging. Effects on lifespan and experimental conditions (e.g. age, gender, nutrient medium, model organism) were then retrieved. Lifespan parameters included average, median, and maximum lifespan and reduced mortality…” so you need to refer to the specific papers reported in the data base to check the precise definition of what authors are actually measuring. I have little time to find more but if you or someone expert in this area finds a good and short resource I would be interested.
https://www.fightaging.org/resources/
http://www.benbest.c...eext/aging.html