blueman,
Let's pick some numbers to see how to calculate your answer. Let's assume you're wonging in with a 2% edge (so at about +5) and flat-betting (so your S.D. is 1.15). If you play 100 rounds, what is the chance you'll be even or ahead?
Well, in 100 rounds, you expect to win 2 units. The total S.D. will be 1.15*?100 = 11.5 units.
If you end up even, your z-score is z = (0-2)/11.5 = -0.17. In general, z = (result - mean)/(standard deviation).
If you consult Table 8.9 on page 147 of BJA3 (or else use the Cumulative Distribution function in, say, Excel), you'll see that the CDF for -0.17 is 0.4325: this means you have a 43.25% chance of being behind. Therefore, you have a 56.75% chance of being even or ahead.
Hope this helps!
Dog Hand
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