<< 
      Graphics`Graphics`


    
countdata  = {103.61, 100.77, 95.09, 92.25, 91.41, 90.18, 90.01, 
          89.39, 89.34, 88.21, 87.15, 86.65, 86.54, 86.39, 85.99, 85.74, 
          85.53, 85.43, 85.12, 84.02, 83.39, 83.14, 82.28, 81.79, 81.66, 
          80.25, 79.1, 78.58, 78.52, 78.41, 78.2, 78.1, 78.01, 77.75, 77.7, 
          77.43, 77.36, 76.76, 76.64, 74.75, 74.67, 74.54, 74.12, 73.8, 
          73.75, 72.47, 72.18, 71.22, 71.11, 71.05, 70.18, 69.78, 69.74, 
          69.66, 69.5, 67.6, 67.23, 67.04, 65.9, 62.05, 61.87, 61.58, 61.29, 
          60.61, 59.6, 59.33, 57.27, 56.4, 55.89, 54.61, 52.28, 51.66, 49.34, 
          48.89, 47.92, 46.64, 42.1, 41.86, 40.7, 38.21, 32.66, 31.37, 30.85, 
          26.89, 25.5, 24.74, 
          22.84};

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]