Good night guys:   Last post i tried to explain an example, but for some logistic reasons i couldn't finish the explanation there so here i go again:   i have this data set:   data have; input id South North east west ; cards; 1 2 4 12 9 2 3 . 11 10 3 2 4 12 10 4 6 4 13 12 ; proc sql; create table want as select *, sum(south + north)/(count(south + north)) as mean_south_north, std(south and north) as sd_south_north from have; quit; proc print data = want; run;, but unfortunately i got this:   Obs id south north west east sum_south_north mean_south_north sd_south_north sum_west_east mean_west_east 1 1 10 . 15 9 116 25.2 8.48528 74 12.3333 2 2 40 12 10 14 116 25.2 8.48528 74 12.3333 3 3 50 14 13 13 116 25.2 8.48528 74 12.3333   The RED BOLD text in the table above represents the standard deviation wrongly found, where the correct value must be  18.4715998224301, as the real value of the standard deviation of 10, 40, 50, 12 and 14. Must be noted that it is a missing value in the data set, so it is very important to consider also.   Other important issue, it would be grate make the program to find the standard deviation from other columns and put them as other variable, for example the standard deviation of west and east observations , as std_west_east, considering GREEN DATA in the table above   i appreciate any help to complete this task correcting the code i provided to you above.   thanks in advance ... View more