How is the Standard Deviation calculated?

[NicholasHolmes]

Hello,

in the analysis of marks for quizzes (eg: https://community.canvaslms.com/t5/Canvas-Resource-Documents/New-Quizzes-Quiz-and-Item-Analysis/ta-p...) the formula for the standard deviation is given.

I am wondering why the population SD is used rather than the sample SD? for samples (i.e., for almost all statistical analysis where you do not have the entire population of data), you should divide the sum of squared deviations by n-1, not by n (https://en.wikipedia.org/wiki/Standard_deviation). dividing by n-1 is the default in (eg) Excel, Matlab, as it should be.

it's a small point, but it's confusing for people who understand statistics and want to see the correct values displayed.

cheers,

Nick (instructor; lecturer in neuroscience, statistics, research methods)