Statistics and Probability / Median and Interquartile Range

Understanding

Dot plots display data in a way that makes it easier to identify the median of a set of data. This knowledge of median is the foundation for understanding interquartile ranges.

What to look for

Students should note that there are the same number of points to the left and to the right of the median; regardless of the shape of the distribution.

Sample Assessment

Identify the following as true or false.

a. The median is the midpoint between the smallest and largest values in the data set. 
Answer: False

b. At most half of the values in a data set have values less than the median. 
Answer: True

c. If you add 10 to every element of a data set, the median will not change. 
Answer: False

d. If you add 10 to every element of a data set, the IQR will not change. 
Answer: True

The Big Idea

Dot plots display data in a way that makes it easier to identify the median of a set of data. This knowledge of median is the foundation for understanding interquartile ranges.

What are the students doing?

Students use dot plots to observe and describe the relationship between the IQR and the median of the distribution of a set of data.

What is the teacher doing?

Counting to the middle of an ordered set of data will give the number such that that half of the values are greater than that number and half are less than that number.