Interpreting the SD

Here is a closer look at the dotplot of Pharmacia stock prices .

           
             .:   .   :  .    .  .. :..    : .    .  .:
           --+---------+---------+---------+---------+-- PHARMACIA
            40.0      45.0      50.0      55.0      60.0

The average is approximately $50. Most individual stock prices are different from $50; the more extreme points (on the outer edges of the plot) deviate by approximately $10, the points closer to center deviate by $2 or $3. The average deviation seems to be around $6 or $7. In fact, the SD is $6.82.