Spread

Spread is the general term for how different the values are. Measures of it are the range (largest minus smallest value), the standard deviation and the interquartile range (width of the middle half).

Example: Concentration: 9 to 88 points, range 79, SD 12.38, interquartile range 17.

Caution: The range depends on only two values. A single outlier (here 9 points) makes it much larger.