I should say im dyslexic so my spelling will be awful. this is a problem for work. I have a set of 30 objects with known mass' if I randomly select a of 10 objects what are the total number of combinations I will get?. I have got 2 answers one of 2.3 x 10^15 the other 30 x10^6 aprox. what formular should I use ? selcondly for every combination im needing to know the standard deviation of every group this will invlove some code can people advise on formulars for calcs of the combinations and the code I would need to produce the std of each indiviudal group.