Standard Deviation. Explain.

[Skybird]

Originally Posted by StdDev

The average amount by which a data point (ie score) deviates from the average of that same set of data points.

or it could mean how twisted the average person actually is

Or in other words: the amount of dispersion (Streuung) of scores from the expected value (Erwartungswert).

One of several additional descriptive values without which any expression of mean values (averages) usually makes little sense.

Started statistics courses?