

Calculate pooled standard deviation f... 

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Rulph S posted on Monday, December 28, 2015  4:03 pm



Hello, I wanted to ask how I can calculate the pooled standard deviation from a TECH4 output? I understand I get the standard deviations by using the square root on each of the measures on the diagonal from the covariance matrix  but how does this lead me to the pooled standard deviation? Specifically, I want to calculate Cohen's d, and substracting the mean of T2 from the mean of T1 is not hard, but what is a simple formula to obtain the pooled standard deviation for the division? For example, I have the following numbers: Mean of T1: 0.000 Mean of T2: 0.063 And on the diagonal: Variance (T1): 0.679 Variance (T2): 0.649 Variance (I): 0.679 Variance (S): 0.414 This leads to... d=(0.0630.000)/???? I would be glad if you could help me with this! 


Because you seem to have the T1 mean fixed at zero only the mean of T2 has variability so no need for pooling. I assume that this concerns time 1 to time 2 change. Just divide by 0.063 by the square root of the T1 variance which tells you how big of a change has taken place in the T1 metric. 

Rulph S posted on Monday, December 28, 2015  4:45 pm



Oh that's great  thanks a lot! So it's just (meanT2meanT1)/sdT1 I'll use that, thanks again. 

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