A sample of 12 students was asked how many hours they had studied the week before their final exam.

Question

Their responses were as follows:

18 40 14 23 14 15 18 14 19 13 16 12

b) find effect on the mean of removing the outlier from the given data.

Answer 1

Looking at this data, the obvious "outlier" is 40.

The mean before removing "40" is (18 + 40 + 14 + 23 + 14 + 15 + 18 + 14 + 19 + 13 + 16 + 12)/12 = 216/12 = 18.

The mean after removing "40" is (18 + 14 + 23 + 14 + 15 + 18 + 14 + 19 + 13 + 16 + 12)/11 = 176/11 = 16.

So the mean drops from 18 to 16 (an 11.1% drop)