search for: sd_a

...ean of C. However for the standard deviation this seems more tricky as it is to assume that standard deviations in A & B correlate. I assume (based on further analysis) a correlation of r =0.5. I found the formula to get the standard deviation of the SUM (not the mean) of two variables: SD=SQRT(SD_A^2 + SD_B^2 + 2*r*SD_A*SD_B) with SD_B and SD_B being the standard deviation of A and B. And r*SD_A*SD_B being the covariance of A and B. Would this formula also be valid if I want to average (and not sum) my two variables? Many thanks for any help & best wishes, Jokel [[alternative HTML ve...

dear experts, I reproduced an experiment (questionnaire) some times. The result of the experiment is a vector of 5 factors, say (A,B,C,D,E). In the original article the result is given in 5 pairs of mean and stDev for A .. E, e.g. mean_A=37.4 and sd_A=8.1. The interval for A,B,C,D,E values is 0..50. The original data frame is not available. For a comparison of my results L=(A',B',C',D',E') with the original G=(A,B,C,D,E) we can interpret that smaller sd-values are 'better'. But for the means the interpretation is a...

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