I'm combining a number of individual observations where I have the mean and standard deviation of each. They are sub-groups of what I'm combining them to. How do I compute the overall standard deviation? I know it's not as simple as averaging the standard deviations. Also, I'd like them weighted based on the size of the mean of each observation. An example of two observations is below, but in many cases I'll have more than two observations to be combined. I have base SAS and SAS Stat available. Mean Standard deviation 11865 3187 1010 658

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