I'm not sure how to find the differences in mean age between groups with standard deviation for a data file formatted in this layout.   Age   Group    Frequency 0         A             27  0         B             42 1         A            109 1         B            22 2         A             65 2         B            72  ...   What I originally did was multiply frequency with age and totaled it, and divided by total frequency for that group, however, I'm not sure if there is a more efficient way.    ... View more