3_04

 

Standard Deviation

    • Standard Deviations represent the spread of a distribution of scores and are the most commonly used standard score
    • They are also the basis for most other standard scores.
    • As discussed in Unit I:
      • Under a bell-shaped curve, 68% of scores fall within one SD of the mean.
      • About 95% fall within two SD’s
      • About 99% fall within three SD’s