Insert a new column in pandas with random string values

I had a DataFrame

     A B C
   0 1 2 3  
   1 2 3 3  
   2 3 2 1  

I needed to create a new column in a pandas DataFrame with 'yes' or 'no' randomly filling this column.

     A B C  NEW
   0 1 2 3  yes
   1 2 3 3  no
   2 3 2 1  no

Using random.choice results in a column with the same result for every line

     A B C  NEW
   0 1 2 3  no
   1 2 3 3  no
   2 3 2 1  no

I tried map, apply and applymap but there's a easier way to do.