Brian;

The final answer is the number of standard deviations the results are, measured from the center of the normal curve.

A negative number is below chance, positives are above chance. If you look the number up in a normal distribution table you'll get a number telling you what fraction of the curve is below your point. I require at least 0.990 to pass, meaning that there's only a 1% chance that the results could have happened by chance.

If you look at a graph of the normal distribution you'll see it's divided up linearly by the standard distributions (x axis) while the curve (y axis) forms a bell shape, highest in the middle tapering off in both directions.

Roger