Kuna kitu kinaitwa 'bias' katika reaserch- kama haujachukua 'random sample' ya watu huwezi ku-conclude kuwa 80% ya women in that country have ever had sex with the presdo! Unaweza ku-conclude kuwa katika sample yako ya 100 women, 80% weshaliwa, ila huwezi ku-generalize kwa wanawake wengine.