Timeline for Intuitive explanation for dividing by $n-1$ when calculating standard deviation?
Current License: CC BY-SA 2.5
9 events
| when toggle format | what | by | license | comment | |
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| Sep 18, 2017 at 14:03 | comment | added | PatrickT | I see, right'o. | |
| Sep 18, 2017 at 12:58 | comment | added | whuber♦ | @Patrick You might be reading too much into my answer, because it is explicit about the reasons: they are pedagogical and have nothing to do with whether $n$ is large or not. | |
| Sep 18, 2017 at 11:11 | comment | added | PatrickT | I thought it could be made explicit in your answer. Instead of just saying that "some books don't bother", I thought you could be explicit about the reason why they don't bother. If you deal with large samples, the adjustment is irrelevant. It is quite intuitive (OP request) to say, "it does not usually make a big difference when $n$ is large." no? | |
| Sep 17, 2017 at 15:00 | comment | added | whuber♦ | @Patrick Yes, that's implicit in all the answers here, I believe: nobody's going to be concerned about the difference when it's tiny. | |
| Sep 16, 2017 at 14:45 | comment | added | PatrickT | For large $n$, there isn't typically much difference between dividing by $n$ or $n-1$, so it would be acceptable to introduce the uncorrected formula provided it was intended to apply to large samples, no? | |
| Oct 24, 2010 at 21:12 | comment | added | Tal Galili | Hi Whuber. Thank you for the vote of confidence :). The loose of the degree of freedom for the estimation of the expectancy is one that I was thinking of using in class. The problem is that the concept of "degrees of freedom" by itself is one that needs knowledge/intuition. But combining it with some of the other answers given in this thread will be useful (to me, and I hope others in the future). Best, Tal | |
| Oct 24, 2010 at 15:40 | comment | added | whuber♦ | @Tal I was writing in your language, not that of your students, because I am confident you are fully capable of translating it into whatever you know will reach them. In other words, I interpreted "intuitive" in your question to mean intuitive to you. | |
| Oct 24, 2010 at 7:15 | comment | added | Tal Galili | Thank you Whuber. I have to teach the students with the n-1 correction, so dividing in n alone is not an option. As written before me, to mention the connection to the second moment is not an option. Although to mention how the mean was already estimated thereby leaving us with less "data" for the sd - that's important. Regarding the bias of the sd - I remembered encountering it - thanks for driving that point home. Best, Tal | |
| Oct 23, 2010 at 22:21 | history | answered | whuber♦ | CC BY-SA 2.5 |