Standard Deviation on TI-83 plus calculator

My list of data is:
762
755
714
660
647
630
612
609
586
583
573
569
563
555
548
536
534
521
521
521

When ever I use the standard deviation thing on my calculator, or solve it by myself, I get two different answers. The calculator says 74.57 and I get 72.68. And I checked over my work so many times and I'm pretty sure I didn't make a mistake. Also, I looked online to try doing this, and both answers came up. I think one said sample and the other was population and I'm not sure what I'm supposed to do. Can someone check my work please or tell me which is right?

That's right—74.57 is the sample standard deviation, and 72.68 is the population standard deviation.

Sample standard deviation most commonly follows the formula:
s = √((∑(i=1, n) [x_i − x̄]²)/(n − 1))

Population standard deviation follows the formula:
σ = √((∑(i=1, n) [x_i − x̄]²)/n)

Which one you need depends on your data. Is that data the data collected from the entire population? Or is it only a small part of the population (a sample)? You'll only be able to tell from the context of the problem.

If you only took 20 of the 1000, then that 20 is a sample, so it should be the sample standard deviation.

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thanks for your help!

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