Question

the mean of 20 observation is 18.if 3 is added to each of the following first 10 numbers then find the new mean of 20 numbers

Answer 1

mean = sum of obs / total
18 = sum/20
360 = sum of 20 obs
when 3 is added to first 10 obs
the no. get 360+30=390
new mean = sum of obs. / total
= 390/20
= 19.5
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