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RolloTomasi · Mar 11, 2009, 12:45 PM

What standard score represents 1.5 and 2 standard deviations below mean?

galactus · Mar 11, 2009, 06:15 PM

Look it up in the z table. Do you have a stats book? The table is surely in there.

Or, you can do it the hard way:

$\frac{1}{\sqrt{2\pi}}\int_{-\infty}^{z}e^{\frac{-t^{2}}{2}}dt$ :):)

If you do not have a table, remember the Empirical Rule says that 34% of the data falls 1 SD below the mean.

Here's the normal graph: You can easily approximate it from looking at the graph.