Descriptive - Freq Distrib

Descriptive - Freq Distrib

1. Techniques to describe the QUANTITATIVE data

   • Quantitative Representation
     • Frequency Distribution
       • Group RAW QUANTATIVE data into mutually exclusive classes
         • HOW to GROUP?
           • 1. Decide on the NO. of CLASSES (k)
             • Purpose is to use enough classes to reveal the basic shape of the data set
               • “2 to the k rule.” such that 2^k > n.
                 • 180 vehicles sold, so n = 180.
                   • If we try k = 7, then 27 = 128, somewhat less than 180. Hence, 7 is not enough classes.
                     • If we let k = 8, then 28 = 256, which is greater than 180. So the recommended number of classes is 8.
             • 2. Determine the class interval or width. (I)
               • Distance btw the MIN value up to the MAX value
                 • Divide the distance over the no. of classes
                   • I = (MAX - MIN) / K
                     • **Round up interval size to MULTIPLE of 10 or 100
                       • Eg. $400
                     • ($3293-$294)/8 = $374.75
               • 3. Set the individual class limits.
                 • Format : UP TO
                   • to avoid overlap the class limits
                 • K * I = Interval RANGE
                   • May be more than the Actual Range
                     • Excess / 2 = A
                       • Subtract A from the MIN value to get a rounded lower limit
                         • $294-$100=$194 round up to $200
                       • $202/2=$101
                     • Eg: $3200 - $2998 = $202
                   • EG: 8 * $400 = $3200
                 • 4. Tally the data into the classes.
                   • 5. Count the no. of items in each class
                     • Thus, EACH class of frequency shld = total observations
                       • Interpret
                         • values tend to concentrate btw $1K and $3K
                           • Highest Frequency: $1800 up to $2200.
                             • 45 observn
                               • Middle of this class is $2K
                                 • Thus, typical profit is $2K