Dear Mike,

Can you do Khan Academy Test #4 Section 4 #23? I was wondering, how do you find Standard Deviation on your calculator (I have the normal TI-84 Plus)?

Pro tip: while your calculator certainly can do it, you will never need to calculate standard deviation to answer a standard deviation question on the SAT. All you need to do is look at the data and figure out which set is more spread out from the mean. In this case, you see that the mean for City A must be right around 79° degrees, since 14 of the 21 days were 79°. All that data is very clustered together around 79°, so the standard deviation will be low.

On the other hand, the mean for City B will be around 78°, even though there were 6 days at 80° and 6 days at 76°. That data is more spread out, so the standard deviation will be higher. Therefore, the answer is B.

It might help to see this data a bit more visually (although you probably wouldn’t do this during your test).

Again, see how the data for City A is really tightly clustered and the data for City B is really spread out? The more spread out the data, the higher the standard deviation.

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