Standard deviation and mean - "combining" the two Lets say one was to have a range of data, with the mean and standard deviations for the different subsets of data. The "best" subset is that with the lowest mean, however how do I include the standard deviation when making my decision. For example, the place with lowest infant mortality has the "best" figures for infant mortality, however how could one include the standard deviation into this, in order to predict where the lowest infant mortality will be next year - assuming that there is no trend over the period of the years (ie. it is NOT slowly decreasing in any place - it is equally likely to be above or below the mean next year). I hope I have explained this well enough, I am open to suggestions. I was thinking of multiplying the standard deviation and mean, but thought that there must be a better statistical method to do this.