Standard Deviation simply calculates how spread out, on average, numbers are away from the mean. Don’t worry too much about the fancy formula. The GRE virtually never tests it, in my experience. I have done one example at the end of video anyway, just in case, to show how to calculate standard deviation.
First secret: Standard Deviation has nothing to do with the median!
Next secret: The Range is only Relevant if the range is zero.
Otherwise you cannot use the range to calculate the standard deviation of a set of numbers.
So how is standard deviation actually tested on the GRE then?
Here is a classic standard deviation GRE ETS question:
Six hundred applicants for several post office jobs were rated on a scale from 1 to 50 points. The ratings had a mean of 32.5 points and a standard deviation of 7.1 points. How many standard deviations above or below the mean is a rating of 48 points?
We will now also cover: What does ‘Within 2 standard deviations’ mean?
It means within 2 standard deviations above OR below the mean.
We will show this, using a bell curve.
Finally, we will calculate an actual standard deviation quantity on a small set of numbers:
4, 5, 7, 11, 13
This will not only be helpful for calculating standard deviation on the GRE 340, but also for gaining some statistics GRE practice. These standard deviation questions, some from ets gre math/ ets gre quant, should help illustrate ways to get a GRE 170 Quant score and achieve 170 GRE Quant.
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