posted by Tanyetta on .
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?
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.