=+18. In the Wright-Fisher model of Example 10.2.6, show that Zn = Xn(1 − Xn)



1 − 1 2m n

is a martingale. Assuming that limn→∞ Zn = Z∞ exists, we have Xn(1 − Xn) ≈



1 − 1 2m n

Z∞ for n large. In other words, Xn approaches either 0 or 1 at rate 1 − 1 2m .