Question

If outlier is removed from the data set $2,3,7,9,6,30$.
The mean of the dataset .

• A. will increase
• B. will decrease
• C. will be same

Answer 1

The correct option is B will decrease

In the given data set, $30$ is an outlier.

The mean of data set with outlier is
$\frac{(2+3+7+9+6+30)}{6}=\frac{57}{6}=9.5$

The mean of the data set without oulier is
$\frac{(2+3+7+9+6)}{5}=\frac{27}{5}=5.4$

Mean without outlier < Mean with outlier
5.4 < 9.5

We can see on excluding outliers, the mean value of the dataset decreased.

$\therefore$ Inclusion of outlier in a dataset always changes the mean value of the data set.