Q. 36

A survey regardin

Answer :

Height (in cm) f C.F.


below 140 4 4


140-145 7 11 1


145-150 18 29


150-155 11 40


155-160 6 46


160-165 5 51


N = 51


N/2 = 51/2 = 25.5


As 29 is just greater than 25.5, therefore median class is 145-150.


Median =


Here, l = lower limit of median class = 145


C = C.F. of the class preceding the median class = 11 1/2


h = higher limit – lower limit = 150 – 145 = 5


f = frequency of median class =18


Median = 145 + 1/2


= 149.03


Mean by direct method


Height (in cm) f xi fxi


below 140 4 137.5 550


140-145 7 142.5 997.5


145-150 18 147.5 2655


150-155 11 152.5 1677.5


155-160 6 157.5 945


160-165 5 162.5 812.5 1


Mean =


= 7637.5/51


= 149.75


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