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I thought it had been shown that SD for SNGs was roughly 1.7 buyins/SNG. Slightly higher for winning players, slightly lower for losing players.
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This doesn't contradict my comments. He just shows that the reasonable range is between 1.5 and 2.
So I'll assume 1.7 and answer the OP's question.
The amount won after 100 games is normal with:
mean = 100*.1 = 10 (the units are buyins)
SD = sqrt(100)*1.7 = 17
The chance of being even or down is therefore about 27%.