Lesson 5: Display Data: Box Plots6.DS.5

I can…

I can make and read a box plot to summarize a data set.

Key words

• Box Plot — A graph that shows how data is spread using five key numbers.
• Median — The middle number when you put them in order.
• Quartile — Numbers that split the data into four equal parts.
• Interquartile Range — The spread of the middle half of the data (Q3 − Q1).
• Data distribution — How the data looks: where it sits and how spread out it is.
• Variability — How spread out the numbers are.

Steps

1. My data, in order: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. There are 11 numbers.
2. The middle number is the 6th one, 14, so the median = 14.
3. The lower half is 4, 6, 8, 10, 12. Its middle is 8, so Q1 = 8.
4. The upper half is 15, 18, 22, 24, 28. Its middle is 22, so Q3 = 22.
5. The lowest is 4 and the highest is 28. I draw a box from 8 to 22, a line at 14, and whiskers out to 4 and 28.

Try it

A box plot has Q1 = 20 and Q3 = 36. What is the IQR and what does it represent?

Check your answer

IQR = 16; it is the spread of the middle 50% of the data

IQR = Q3 − Q1 = 36 − 20 = 16. The IQR tells you the range of the middle 50% of the data.

Sentence starter

I know ___ because ___.

Goal: I can explain my box plot using the words box plot, median, quartile, and interquartile range.