Question

Here are 10 test scores: 30, 74, 76, 77, 78, 79, 80, 80, 82, 84. The mean of these scores is 74.

Does this set have an outlier and, if so, how does removing it affect the mean?



A.
The set has 30 as an outlier and removing it decreases the mean by about 10.


B.


This data set has no outliers.


C.
The set has 30 as an outlier and removing it increases the mean by about 5.


D.
The set has 30 as an outlier and removing it decreases the mean by about 5.

Answer 1

We add up all those numbers (excluding 30) and divide by the number of numbers (9). This results in 78.8 (round up to 79).

79-74 = 5. So the mean has increased by 5 points. (C)