Jinsi ya kupima iq ya mtu. (intelligence quotient)

guys nimekuwa nikisikia kuwa kuna watu fulani wana IQ kubwa, yaani great thinkers compared to others.
sasa ni kitu gani kinachoweza kusababisha mtu kuwa na IQ kubwa kuliko wengine ?

and please lets suggest how to improve people's IQ's.

en.m.wikipedia.org/wiki/Intelligence_quotient