Standard deviation spreadsheet - unexpected result

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Good answer! Some background may still be in order.

There is a reason why the STDEV() "sample standard deviation" differs from the STDEVP() "population standard deviation".

"How much variation is there?"

STDEVP() is meant to be used if you have a dataset which encompasses the entire population in question. It is a determined value.

"What uncertainty is there to my statistical analysis"

STDEV() is meant to be used for a sample set. The (n-1) divisor gives a larger result, which signifies an added insecurity, represented numerically by what you may think of as an "inflated deviation". It is an approximation which depends on the selection of the sample set. The "inflating" diminishes if you take a larger set of samples.

@Meneer, you answered

... I am aware of the difference between population and sample standard deviation. ...

Please accept my apologies!

Of course you would be aware of that, given that you are teaching a subject where this is an element. I must read my audience better, it seems. No offense was intended by my previous comment. My bad!

I still leave that elaboration as it stands, seeing that it just might be useful to other users searching for similar subjects.