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Quartiles Percentiles

Cumulative Frequency Graph

Cumulative frequency graph is drawn using values in x axis and cumulative frequencies in y axis.

Quartiles divide the total frequency into 4 equal parts.

Quartiles are denoted by

Q₁ – First or Lower Quartile.

Q₂ – Second Quartile or Median.

Q₃ – Third or Upper Quartile.

Inter Quartile Range = Q₃ – Q₁

Box and whisker plot is drawn using lowest value, highest value and three quartiles.

Box is drawn using three quartiles.

Lines are drawn from either side of the box to the lowest value and highest value.

Σf/4 = 120/4 = 30

Draw a horizontal line from 30 to touch the graph.

Draw a vertical line from this point to meet the X axis at the First Quartile, Q_1.

Similarly find Q₂ and Q3.

Percentiles divides the total frequency into 100 equal parts.

Percentiles are denoted by

P₁, P₂, P₃,…,P_99.

P₅₀ – 50^th Percentile is the Median.

50Σf/100

= 50x120/100 = 60.

Draw a horizontal line from 60 to touch the graph.

Draw a vertical line from this point to meet the X axis at the 50^th percentile, P_50.

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