Q10 of 44 Page 80

Mean of 100 observations is found to be 40. At the time of computation two items were wrongly taken as 30 and 27 instead of 3 and 72. Find the correct mean.

Given that, the total number of observations = 100

Mean of 100 observations = 40


Mean is given by,



⇒ Sum of all observation = Mean × Total number of observations


⇒ Sum of all observation = 40 × 100 = 4000


Now, according to the question, two items in the observation were wrongly taken as 30 and 27 instead of 3 and 72.


So, in order to obtain the new mean, we need to subtract 30 and 27 from the sum of observations and add the correct values, 3 and 72 to it.



⇒


⇒


Thus, the new mean = 40.18


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