## The probability of winning

To get the probability of winning, first we compute the distribution of the goal differential:

```    goal_dist1 = MakeGoalPmf(suite1)
goal_dist2 = MakeGoalPmf(suite2)
diff = goal_dist1 - goal_dist2```

The subtraction operator invokes `Pmf.__sub__`, which enumerates pairs of values and computes the difference. Subtracting two distributions is almost the same as adding, which we saw in Addends.

If the goal differential is positive, the Bruins win; if negative, the Canucks win; if 0, it’s a tie:

```    p_win = diff.ProbGreater(0)
p_loss = diff.ProbLess(0)
p_tie = diff.Prob(0)```

With the distributions from the previous section, `p_win` is 46%, `p_loss` is 37%, and `p_tie` is 17%.

In the event of a tie at the end of “regulation play,” the teams play overtime periods until one team scores. Since the game ends immediately when the first goal is scored, this overtime format is known as “sudden death.”

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