Are any of the following values outliers? 3 5 8 1 4 11 3 1 18

11 and 18, 18 if it's only one option

It appears that the only major outlier of this set of numbers could be is 18 but that is incorrect. The answer is none.

An outlier in a distribution is a number that is more than 1.5 times the length of the box away from either the lower or upper quartiles. Specifically, if a number is less than Q1 - 1.5*IQR or greater than Q3 + 1.5*IQR, then it is an outlier.

Basically 18 appears to be inside the box and so does 1