Draw 'less than ogive' and 'more than ogive' on a single graph paper and hence find the median of the following data:


Class



5 - 10



10 - 15



15 - 20



20 - 25



25 - 30



30 - 35



35 - 40



Frequency



2



12



2



4



3



4



3


The frequency distribution table for ‘less than’ type is:


CLASS



CUMULATIVE FREQUENCY (Cf)



Less than 10



2



Less than 15



2 + 12 = 14



Less than 20



14 + 2 = 26



Less than 25



26 + 4 = 30



Less than 30



30 + 3 = 33



Less than 35



33 + 4 = 37



Less than 40



37 + 3 = 40



The frequency distribution table for ‘more than’ type is:


CLASS



CUMULATIVE FREQUENCY (Cf)



More than 5



28 + 2 = 30



More than 10



16 + 12 = 28



More than 15



14 + 2 = 16



More than 20



10 + 4 = 14



More than 25



7 + 3 = 10



More than 30



3 + 4 = 7



More than 35



3



Plotting points for ‘less - than ogive’ and ‘more - than ogive’ on the graph,



In this type of graph where ‘less than ogive’ and more than ogive’ are plotted in the same graph, median is found on x - axis by the intersection of these two ogives.


Here, median = 15.5


20