<< 
      Graphics`Graphics`


    
countdata  = {104, 97, 83, 103, 76, 87, 74, 56, 82, 87, 81, 77, 92, 
          77, 82, 79, 68, 79, 74, 53, 79, 101, 65, 54, 68, 76, 47, 74, 61, 
          67, 79, 79, 46, 66, 50, 66, 54, 74, 56, 54, 62, 62, 56, 67, 53, 61, 
          65, 58, 62, 69, 52, 44, 69, 65, 56, 43, 40, 57, 71, 44, 68, 68, 41, 
          61, 54, 44, 34, 45, 46, 42, 40, 45, 36, 39, 41, 29, 31, 45, 39, 25, 
          20, 29};

Histogram[countdata, 
      HistogramCategories -> {0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 
          100,  110,  120}]

less50  = 
        Select[countdata,  (# < 50)  &];
Length[less50]

fifty2sixty  =  
        Select[countdata, ( (# < 60) &&  (#  ≥  
                    50)) &];
Length[fifty2sixty]

sixty2seventy =  
        Select[countdata, ( (# < 70) &&  (#  ≥  
                    60)) &];
Length[sixty2seventy]

seventy2eighty =  
        Select[countdata, ( (# < 80) &&  (#  ≥  
                    70)) &];
Length[seventy2eighty]

eighty2ninety =  
        Select[countdata, ( (# < 90) &&  (#  ≥  
                    80)) &];
Length[eighty2ninety]

greater90  =  
        Select[countdata,  (# ≥  
                90) &];
Length[greater90]