Statistics and Probability / Outliers

Understanding

Outliers are values that lie outside 1.5 IQR values from the upper or lower quartile in a box plot.

What to look for

Students should recognize that outliers have no impact on the median and interquartile range.

Sample Assessment

To find an outlier you need to know?

I. The median
II. The minimum and maximum
III. The quartiles

a. All of the above
b. I and III
c. II and III
d. I and II

Answer:  C

The Big Idea

Outliers are extreme data values, worth noting for contextual reasons and for their effects on center and spread.

What are the students doing?

Students identify outliers visually and using the formula; noticing the impact of outliers on the mean and mean absolute deviation.

What is the teacher doing?

Encourage students to think of plausible explanations for outliers in the context of the data.