In a hospital, the ages of diabetic patients were recorded as follows. Find the median age.


Age (in years)



0 - 15



15 - 30



30 - 45



45 - 60



60 - 75



Number of patients



5



20



40



50



25


To find median,

Assume Σfi = N = Sum of frequencies,


h = length of median class,


l = lower boundary of the median class,


f = frequency of median class


and Cf = cumulative frequency


Lets form a table.


AGE(years)



NUMBER OF PATIENTS(fi)



Cf



0 - 15



5



5



15 - 30



20



5 + 20 = 25



30 - 45



40



25 + 40 = 65



45 - 60



50



65 + 50 = 115



60 - 75



25



115 + 25 = 140



TOTAL



140




So, N = 140


N/2 = 140/2 = 70


The cumulative frequency just greater than (N/2 = ) 70 is 115, so the corresponding median class is 45 - 60 and accordingly we get Cf = 65(cumulative frequency before the median class).


Now, since median class is 45 - 60.


l = 45, h = 15, f = 50, N/2 = 70 and Cf = 65


Median is given by,




= 45 + 1.5


= 46.5


Thus, median age is 46.5 years.


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