4.4 Understanding histograms and boxplots
An Australian study (Lunn and McNeil 1991) compared the dimensions of jellyfish at two sites at Hawkesbury River, NSW (Dangar Island; Salamander Bay) to determine how the jellyfish were different at each site.
A histogram of the breadth of jellyfish at Dangar Island Bay is shown in Fig. 4.3.
- Two students are arguing about the median breadth.
Student 1 says:
The bars in the histogram have heights of 10, 2, 4, 2 and 4.
When these numbers are put in order, they are: 2, 2, 4, 4, 10.
The median breadth is the median of these numbers, so the median breadth is the middle one: 4mm is the median.
Student 2 responds:
You have the correct answer, but for the wrong reason!
There are five bars, and the middle bar is the third bar.
Since the third bar has a height of 4, the median breadth is 4mm.
Who is correct? Explain.
Describe the histogram.
Describe and compare the breadths of the jellyfish.