Calculate 2 standard deviations
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I am trying to calculate +/- two standard deviations from the mean of a bunch of values. I am not sure if I am using the standard deviation function properly. Would I just multiply by two to get 2 standard deviations?
dmean = mean(values(:,1)); upperstd = dmean+2*std(values(:,1)); lowerstd = dmean-2*std(values(:,1));
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Wayne King
2011년 8월 28일
Hi Chris, for a matrix of data
x = randn(10,4);
mean(x)+2*std(x)
mean(x)-2*std(x)
gives the sample means of the columns plus/minus 2 times the standard deviation. The question is whether you really want the sample standard deviation here, or the standard error of the mean.
Wayne
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jay yawson
2019년 6월 17일
Hello Wayne King. In this case, how would you calculate the standard error of the mean?
Thomas To
2020년 1월 20일
Jay, the standard error is calculated by taking the standard deviation and dividing it by the square root of N-th samples used to calculate the standard deviation.
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