proc means

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#What is the difference between class and by statement
   you don't have to sort the data before using class variable
#Proc means vs proc summary
  you don't need noprint option in proc summary .it is default
# How will  you find number of missing observations in proc means
   using NMISS in OUTPUT statement
# What is the autoname used in output statement.
   label names are automatically generated with outoname
#We know that grand mean is default with class statement how to get rid of grand mean
   with NWAY in PROC MEANS statement
# How you will compute the means and number of nonmissing values of two variables a and b
   for each combination of other two variables x and y.
   have to use multiple class variables with
   class x y;
var a b;
#How do you test for missing values?
  Use PROC MEANS to count the missing values for each variable
  proc means data=sasdsn nmiss noprint;
  output out=missdsn(drop=_type_ _freq_) nmiss=;
  run;