From Wikipedia:
Human life expectancy is a statistical measure of the estimate of the average remaining years of life at a given age.
What you described would be the median, not average. Those can be very far apart, a good example is the distribution of wealth. Put 10 homeless people in a room with Bill Gates and everyone’s a billionaire on average.
Average life expectancy can be misleading. I did the maths with my grandfather’s siblings and him, they had an average life expectancy of like 50. However two died before their first birthday, one died shortly after, then the next one to die was like 58, and the rest were 80-90.
The median is an average. There’s generally three types of average, Mean (what you’re talking about), Median (the one they’re talking about), and Mode (the one rarely talked about).
Average has a definition of being the mean, median, or mode, BUT it also has a definition that it is a synonym for the mean.
Sorry for being nitpicky and thanks for naming them all. I just assume the term average is equivalent to mean average in peoples heads. For uneven distributions, like wealth or life expectancy are I assume, mean average in itself just wouldn’t be a useful measurement.
Yes, when most people say average, they mean mean. Few people I’ve met know the other concepts even exist.
Even Excel has a function called “average”, whereas R uses the “mean” function for the same thing. Interestingly, R doesn’t have a function called “average”, because that term is far too ambiguous to statisticians. I think that summarizes pretty well who these tools were made for.
US public schools taught me that mean=average and the others were themselves, not that average describes any process to find a “normal” value. Just throwing that out there so people know why the conversation above happens so frequently.
The very wiki article quoted says average to mean mean (made explicit later). OP showerthought was calculating life expectancy in a way different than commonly understood. The first nitpick was correct.
deleted by creator
Interesting proposal, but I’m thinking it might not be necessarily so. Life expectancy is an average, and averages do not need to be exactly at 50% of the population. That’s the median, you are thinking of the median. It is quite more complicated than that, as there are hundreds of factors that alter life expectancy, thus there are many life expectancy tables depending on gender, lifestyle, cohort, race, income, etc. It will not amount to 50% of the population, specially for populations with a lot of outliers. People who die soon after birth or live exceptionally long lives will skew the average deviating it from a true central tendency. As people live longer and less people die early, then the median (the age at which at least 50% of a cohort, people born the same year, dies) will shift away from the average and occur later. If a lot of teenage and young people die, but the survivors live long lives, then the median will occur sooner. The technical terms are skewness and kurtosis of a probability distribution.
This changes in statistic sources will alter probabilities and thus life expectancy will not correlate directly with the median.
