Determine the mean of the following distribution


Here, we observe that, 5 students have scored marks below 10, i.e. it lies between class Interval 0 - 10 and 9 students have scored marks below 20.

So, (9 – 5) = 4 students lie in the class interval 10 - 20. Continuing in the same manner, we get the complete frequency distribution table for given data.



Here, (assumed mean) , a = 45


and (class width) h = 10


By step deviation method,




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