Plotting standard deviation function using WolframAlpha

Asked Nov 28 '15 at 15:38

Active Nov 28 '15 at 15:38

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I'm trying to plot a standard deviation function using WolframAlpha's function plotter and my function looks like this:

$SD(Y) = \sqrt{\sum_{i=2}^{k}\frac{k(i-1)}{ (k-(i-1))^2 }}$ where k goes from 1 to 50.

And I've written my function like this in the plot

plot sum( (k(i-1)) / ((k-(i-1))^2) ) from i=2 to k from k=1 to 50

But I can't seem to put a square root over the whole sum without an error. How can I write my standard deviation function and get the graph?

asked Nov 28 '15 at 15:38

Nubcake

1

Sometimes with wolfram alpha, you have to use wolfram language input. Like this – Ben Longo Nov 28 '15 at 15:52
Thanks, I didn't know such a thing existed – Nubcake Nov 28 '15 at 15:54
If you look at your original input of sum( (k(i-1)) / ((k-(i-1))^2) ) from i=2 to k and click on the 'A' symbol, use the Wolfram Language plain text input. – Ben Longo Nov 28 '15 at 15:56
Sorry I don't see the 'A' symbol, where is it? – Nubcake Nov 28 '15 at 16:00
when you hover you mouse over the Sum: box, there will be an A symbol below with a list of other options. – Ben Longo Nov 28 '15 at 16:02
Ok yes I see it now – Nubcake Nov 28 '15 at 16:03

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