Posted by **Tanyetta** on Monday, October 22, 2012 at 8:49pm.

A shaded area reprsents approximately 95% of the scores on a standardized test. If these scores ranged from 78 to 92, whic could be the standard deviation?

- Math -
**PsyDAG**, Tuesday, October 23, 2012 at 2:31pm
I don't know what area is shaded.

If it is symmetrical around the mean, then 95% of the scores are within a Z score of 1.96 in either direction. (Since it says approximate, you could round it off to 2.) The mean is (78+92)/2 = ?

Z = (score-mean)/SD

Insert the values and solve for SD.

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