Key words
     frequency table, bar chart ,range
     width of interval , mid-interval
     Histogram , Polygon
                      Text Book  :   Basic Concepts and 
                        Methodology for the Health 
                            Sciences                    2
      Organizing The Data
  A table showing the classes and the frequency of occurrence 
  of their elements is called a frequency distribution
  1- Ungrouped (or Simple) frequency distributions : 
       Used for:
  ·       - qualitative variables
  ·    - discrete quantitative variables with a few different values
  2- Grouped frequency distributions :
  Used for:
  ·       - continuous quantitative variables
  ·    - discrete quantitative variables with large number of different values    
       Descriptive Statistics
             2.1 Frequency Distribution 
             for Discrete Random Variables
 Example  1:                      Frequency           No. of 
 Suppose that we take a                           decayed teeth
 sample of size 16 from 
 children in a primary school 
 and get the following data 
 about the number of their             1                 0
 decayed teeth,                        2                 1
 3,5,2,4,0,1,3,5,2,3,2,3,3,2,4,1       4                 2
 To construct a frequency              5                 3
 table:                                2                 4
 1- Order the values from the          2                 5
 smallest to the largest.
 0,1,1,2,2,2,2,3,3,3,3,3,4,4,5,5
 2- Count how many                     16              Total
 numbers are the same.
                      Representing the 
         simple frequency table 
                  using the bar chart
  We can represent                                        6
  the above simple 
  frequency table                                         5
  using the bar                                                                                5
  chart.                                                  4
                                                                                     4
                                                          3
                                                          2
                                                                            2                           2        2
                                                        y
                                                        c 1
                                                        n
                                                        e          1
                                                        u
                                                        q
                                                        e
                                                        r
                                                        F 0
                                                                  .00      1.00     2.00      3.00     4.00     5.00
                                              Text Book  :   Basic Concepts and 
                                                 Methodology for the Health 
                                                           Sciences                                                   5
                                                            Number of decayed teeth
          Simple frequency, relative  frequency and percentage 
                 frequency  distribution of the no. of children
           No. of decayed         Frequency           Relative Freq. (R. F.)   Percentage Freq.
                teeth                                          (r=Freq /n)     (= R.F. * 100%)
                  0                  1                    0.0625                    6.25%
                  1                  2                     0.125                    12.5%
                  2                  4                     0.25                      25%
                  3                  5                    0.3125                   31.25%
                  4                   2                    0.125                    12.5%
                  5                   2                    0.125                    12.5%
               Total               n=16                    1.00                     100%
               Note
               1.Total of the frequencies = n =  sample size.
               2.Relative frequency = frequency/n=r.
               3.Total of the Relative frequencies=1.
               4.Percentage frequency = Relative frequency *100%.
               5.Total of Percentage frequency = 100%.