The average height of a Russian citizen is 177.2 cm. 80.9% of Russians are ethnic Russians. Is it possible to infer the average height of an ethnic Russian (who is also a Russian citizen), and if it is, what is it?
This question interests me, but I have no formal mathematics education beyond highschool, so I cannot hope to answer it. Any help is much appreciated.
If there isn't any additional data given, there is no way to answer this question. We can't deduce the average height of ethnic Russians, because we don't know if the rest of the Russian citizens are higher or lower on average.
Suppose that the average height of a Russian citizen which isn't ethnic Russian is 200cm. Then we'd find that ethnic Russians aren't very high on average (171.8 cm). On the contrary if the average height of a Russian citizen which isn't ethnic Russian is 160cm then we'd find that the ethnic Russians' average height is pretty high (181.3 cm).