The national mean for verbal scores on an exam was 428 and the standard deviation was 113. Approximately what percent of those taking this test had verbal scores between 315 and 541?

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- Nov 16th 2008, 09:44 PMmagentaritaVerbal ScoresThe national mean for verbal scores on an exam was 428 and the standard deviation was 113. Approximately what percent of those taking this test had verbal scores between 315 and 541?
- Nov 16th 2008, 10:22 PMTitaniumX
$\displaystyle (315 < X < 541)$

$\displaystyle (\frac {315-428}{113} < Z < \frac {541-428}{113})$

$\displaystyle (-1 < Z < 1)$

Phi(1) - Phi(-1) = 0.8413-0.1587 = 0.683 =**68.3% is your answer**

Also, since it's 1 standard deviation from the mean, we didn't have to calculate it. It's always about 68.3%. 2 SD from the mean is roughly 95%. - Nov 17th 2008, 10:14 PMmagentaritaok.......