What is the average age of residents of San Francisco, CA?

Median age is 40

http://factfinder.census.gov/servlet/ACSSAFFFacts?_event=&geo_id=16000US0667000&_geoContext=01000US|04000US06|16000US0667000&_street=&_county=san+francisco&_cityTown=san+francisco&_state=04000US06&_zip=&_lang=en&_sse=on&ActiveGeoDiv=geoSelect&_useEV=&pctxt=fph&pgsl=160&_submenuId=factsheet_1&ds_name=null&_ci_nbr=null&qr_name=null&reg=null:null&_keyword=&_industry=

“Median Age: This measure divides the age distribution in a stated area into two equal parts: one-half of the population falling below the median value and one-half above the median value.”

Welcome to Fluther

The answer you got from @bpeoples is likely to be the best one you will get as a “measure of central tendency” for the data set “San Francisco resident ages”. As you may already know (but some other readers may not) there are three primary measures of central tendency in population samples:
– mean (or average) as you have requested – this would be the sum of all ages of San Francisco residents divided by the number of people

- median – this is the ‘middle age number in years’ of the list of ‘all ages of all residents’ in an ordered list

- mode – this is ‘the age that occurs most often’ in the list of ‘all ages of all residents of San Francisco’

Since US Census data is about the best data you’ll find for this request, and since the extract only shows “median age”, I wouldn’t expect a better response.

The median age will be one closer to 22 once I move there in January!

@CyanoticWasp While I understand the mechanics of median vs. mean how different would one expect the ages to be?

@bpeoples it all depends on the population and distribution of ages.

For extreme examples, look at the ages of “all people in a grade school” and “all people in a retirement home”. In each of those places the average / mean age (because the grade school has teachers and office workers much older than the students, and the retirement home has nurses and administrators who are much younger than the resident population) may be quite a bit different from the median or mode.

But in a place as non-specific as a metropolitan city, I’d expect all three of these numbers, mean, mode and median, to be relatively close together. That’s why all of these “measures of central tendency” should be looked at together when they can be, to get an idea of “what really is the ‘central tendency’ here”.