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# standard deviation in errorbar

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Sim on 3 Mar 2021
Commented: Star Strider on 3 Mar 2021
[a very silly question!] How to calculate the errorbar with 2 standard deviations in this example?
x=1:10;
y=rand(10,50);
errorbar(x, mean(y,2), std(y,[],2)) % 1 standard deviation
Just multiplying std by 2 in the errorbar, right?
errorbar(x, mean(y,2), 2 * std(y,[],2))
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### Accepted Answer

Star Strider on 3 Mar 2021
Not silly at all, however it may not produce the result you want.
It might be more appropriate to calculate the errors as the standard error of the mean (S.E.M.) :
err = 2*(std(y,[],2)/sqrt(size(y,2))); % 2 x Standard Error Of The Mean
then:
figure
errorbar(x, mean(y,2), err) % 2 standard errors of the mean
rather than the standard deviation of the observations themselves.
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Star Strider on 3 Mar 2021
@Rik I very much appreciate your compliment!

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