When reading passages like the following:

Based on a representative sample of 88 recent raids, we show that the Turkana sustain costly cooperation in combat at a remarkably large scale, at least in part, through punishment of free-riders.

I wonder what ‘representative sample’ might refer to.

Is it related to power calculations (for example) in statistical inference or is there some way to assess the number of samples required from the total population for it to be considered representative?

**Answer**

A representative sample is one which is drawn without bias from the population of interest.

For example, suppose I want to find out how many people drink milk with breakfast. If I am a vegan, and I ask a random sample of my friends and associates (many of whom are also vegans), then the sample I have taken is not representative of the population as a whole: I will of course find that a low proportion of people drink milk with breakfast, but this is an artifact of my choice of sample, not because so few people do in reality.

Basically, if there’s any factor which causes us to select our sample in a non-random way, the inference is questionable. In the example above, a representative sample is one drawn randomly from *all* raids. We could also draw samples only during winter, in which case we might get a skewed result (maybe the cold makes people less prone to cooperation).

Hope that clears things up a bit…

**Attribution***Source : Link , Question Author : upabove , Answer Author : John Doucette*