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Pooled mean and standard deviation

version 1.10 (1.53 KB) by

Calculate pooled N, mean and STD (using, as inputs, subgroups N, mean and STD)

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Calculate pooled n, mean and std from n, mean and std of two groups
 (to calculate it to N groups (N>2), repeat it N-1 times)
[npool,meanpool,stdpool] = pooledmeanstd(n1,mean1,std1,n2,mean2,std2)

based on http://www.talkstats.com/showthread.php/7130-standard-deviation-of-multiple-sample-sets

Example:

    n1=32;
    sample1 = randi(100,n1,1);
    mean1= mean(sample1);
    std1= std(sample1);
    n2=20;
    sample2 = randi(100,n2,1);
    mean2= mean(sample2);
    std2= std(sample2);
    n3=9;
    sample3 = randi(100,n3,1);
    mean3= mean(sample3);
    std3= std(sample3);
    pool_sample=[sample1;sample2;sample3];
    meanpool_real= mean(pool_sample);
    stdpool_real= std(pool_sample);

    [npooltemp,meanpooltemp,stdpooltemp] = pooledmeanstd(n1,mean1,std1,n2,mean2,std2);
    [npool_estimated,meanpool_estimated,stdpool_estimated] = pooledmeanstd(npooltemp,meanpooltemp,stdpooltemp,n3,mean3,std3);

    disp(['meanpool_real=',num2str(meanpool_real),' meanpool_estimated=',num2str(meanpool_estimated)])
    disp(['stdpool_real=',num2str(stdpool_real),' stdpool_estimated=',num2str(stdpool_estimated)])

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1.10

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1.5

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