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# Pooled mean and standard deviation

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### R P (view profile)

19 Jun 2012 (Updated )

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

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Description

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)

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)])

MATLAB release MATLAB 6.5 (R13)
20 Jun 2012 1.1

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10 Dec 2012 1.5