Q5 of 25 Page 346

The following table gives the distribution of the life-time of 400 neon lamps


Find the median life time of a lamp.


For median:


We have, total frequency, N = 400


N/2 = 400/2 = 200


Observe, cf = 216 is just greater than 200.


Thus, median class = 3000-3500


Median is given by



Where,


L = Lower class limit of median class = 3000


N/2 = 200


cf = cumulative frequency of the class preceding median class = 130


f = frequency of the median class = 86


h = class interval of the median class = 500


Substituting these values in the formula of median, we get



⇒


⇒ Median = 3000 + 406.98


⇒ Median = 3406.98


Thus, the median is 3406.98 hours.


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