 Suppose that Player I plays L, Player II plays l2 and Player III plays l3. Suppose also that μ(II) assigns pr(.3) to node 16. In that case, l2 is not a SE strategy for Player II, since l2 returns an expected payoff of .3(4) + .7(2) = 2.6, while r2 brings an expected payoff of 3.1. Notice that if we fiddle the strategy profile for player III while leaving everything else fixed, l2 could become a SE strategy for Player II. If §(III) yielded a play of l3 with pr(.5) and r3 with pr(.5), then if Player II plays r2 his expected payoff would now be 2.2, so (Ll2l3) would be a SE. Now imagine setting μ(III) back as it was, but change μ(II) so that Player II thinks the conditional probability of being at node 16 is greater than .5; in that case, l2 is again not a SE strategy.