Quote:
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?