W - 3: SOLVE & INTERPRET QUARTILES(GROUPED DATA)

• Quartiles


  Measures of position that divide a set of data into four equal parts
• Grouped data


  Data formed by aggregating individual observations of a variable into groups, so that a frequency distribution of these groups serves as a convenient means of summarizing or analyzing the data
• Frequency distribution table shows the class intervals, scores, and frequency
• Lower boundary (LB)


  The lower limit of each class interval
• Less than cumulative frequency (<cf)


  The cumulative frequency up to the class before the current one
• Formula for quartile


  Qk class = kn/4

  Qk = LB + (kn/4 - <cfb) / fQk * i

  LB = lower boundary of the Qk class

  n = total frequency

  <cfb = less than cumulative frequency before the Qk class

  fQk = frequency of the Qk class

  i = size of the class interval

  k = nth quartile