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### Course: Get ready for AP® Statistics>Unit 2

Lesson 2: Box and whisker plots

# Worked example: Creating a box plot (odd number of data points)

A box-and-whisker plot is a handy tool for visualizing data. By ordering numbers, we can find the range, median, and quartiles. Practice makes perfect when mastering these concepts!

## Want to join the conversation?

• can you give me some practice problems? what happened to those?
• I still don't really understand how to create box plots. Can someone help me understand please.
• 1) Order numbers from least to greatest
2) Find median, if there is an even number of values take the mean of the middle 2
3) Q1 is the middle value between median and lowest value. If there is an even number of values in between median and lowest value, then take mean of the middle 2. Do the same with the upper half to find Q3.
4) Draw it out over a number line
• cant understand what exclude the median means
• When you calculate the 1st and 3rd quartile values, count after the median to the endpoint.

In the even number example, you start counting all the numbers in each half which includes 7 numbers for this example. So you find the middle of that grouping.

in the odd number of objects example, the median is an actual number. When counting out the quartile, you ignore that one
• Whatever happened to the exercise shown is the video? It looks great practice for this skill!
• Why do you show examples before defining what is being explained?
You jump right into a box-and-whisker plot example without even a brief explanation of what the box-and-whisker plot is.
Having watched the example, it is a simple concept and the example was enough to explain it - still a brief summary before launching into an example would be nice.
• Thanks for the help
• Suggestion regarding meaning of words, such as "top of Q1" could also be called "beginning of Q2." This has been confusing me when you say Q3 minus Q1. Please say what is range from beingging of Q2 to end of Q3. Don't use "top of" use beginning of"
• I am not sure I have understood your question.

Q3 is the 75th percentile and Q1 is 25th percentile. Basically you take the median and then take media again.

We could regard the beginning of the 2nd quartile as the top of quartile 1. As both these are the 25th percentile. I guess it is matter of preference.

Basically Q1, Q2 and Q3 are already defined. But each quartile represents 25% of the data. So they are different concepts.
(1 vote)
• I'm confused, isn't it standard not to include the median in the IQR unless the number of data points is even? Why does it say not to include the median in the IQR in the exercise if that is standard procedure (in this case)?
• It's just a reminder.