Andrew Griffin · @andygriffwozere
15th Sep 2011 from Twitlonger
@RTaylorUK Yes, John's right; the rate of stop-and-searches 'acted on' (that is arrested) is constant between both black stop-ees and white stop-ees. So let's call that y (let's assume it's 0.5; half of people stopped are arrested). Amount of people arrested following stop and search depends, then, on how many are stopped*. So let's call the amount of searches n.
Amount of arrests will = n x y.
In the case of black people, n is twice as high. 2n. Let's call amount of black people arrested 'b', and amount of white people arrested 'w'.
SO
w = 2b. Yes. But only because in the case of black people, 'n' is also twice as large.
WHICH IMPLIES
that if 'n' remained the same - both numbers would be equal. Remember n and y both remain constant:
n x y = w
n x y = b
b = w.
Does this make sense now?
*Obviously this isn't entirely true -- if the police went round stopping everyone y would decrease -- but it doesn't actually matter.