MATLAB Answers

# How to do paired t test with mean and sd?

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Rita on 29 Aug 2016
Commented: Star Strider on 30 Aug 2016
I would like to do paired t-test with mean and standard deviation and the number of sampling.
for A:mean =8.37 sd=0.53
B: mean=8.18 sd=0.16 number of samples for both A=B=44
Thanks.

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### Accepted Answer

Star Strider on 30 Aug 2016
To do it with only the means and standard deviations, you would have to write your own functions to calculate the one- and two-tailed t-probabilities, but fortunately with MATLAB that is not difficult:
Amean =8.37;
Asd=0.53;
Bmean=8.18;
Bsd=0.16;
N = 44;
v = 2*N-2;
tval = (Amean-Bmean) / sqrt((Asd^2+Bsd^2)/N); % Calculate T-Statistic
tdist2T = @(t,v) (1-betainc(v/(v+t^2),v/2,0.5)); % 2-tailed t-distribution
tdist1T = @(t,v) 1-(1-tdist2T(t,v))/2; % 1-tailed t-distribution
tprob = 1-[tdist2T(tval,v) tdist1T(tval,v)]
tprob =
0.0253 0.01265
So your groups are significantly different at alpha = 0.05.
The functions are correct, but you may want to check my ‘v’ and ‘tval’ calculations to be certain it they are correct to your experimental design. If they are not, change them appropriately.

#### 2 Comments

Rita on 30 Aug 2016
You are amazing! Thanks
Star Strider on 30 Aug 2016
Thank you! My pleasure!

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### More Answers (1)

Thorsten on 30 Aug 2016
Edited: Thorsten on 30 Aug 2016
If you have the Statistics Toolbox, you can use
ttest(A-B)

#### 2 Comments

Rita on 30 Aug 2016
Thanks a lot.I have this toolbox but can ttest function work with mean and sd without samples? Thanks again
Thorsten on 30 Aug 2016
No, you need the samples.

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