What is standard deviation?

Document created by Community User on Oct 31, 2017Last modified by Community User on Oct 31, 2017
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What is standard deviation?

Answer
The standard deviation indicates how much the ability estimates are spread out for a group of students. The higher the number, the more diverse the instructional levels are within that group; the lower the number, the more the students are alike. This number can help teachers determine how effective whole group instruction might be within their class. If all the scores were the same, the standard deviation would be zero. Typically, most (but not all) students will be within one standard deviation from the mean or average RIT score for the group.

In the NWEA Norms Study, since RIT scores for all students in the study are normally distributed, approximately 68% of the scores are within one standard deviation from the mean RIT score for a grade.

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