Box and Whisker Plots

1. Box and Whisker Plots An interactive lesson

2. Introduction • A box-and-whisker plot can be useful for handling many data values. • They allow people to explore data and to draw informal conclusions when two or more variables are present. • It shows only certain statistics rather than all the data. • Box and whisker plots consists of the median, the quartiles, and the smallest and greatest values in the distribution.

3. How to make a Box and Whisker Plot • Put your set of date in increasing numerical order (if it isn’t already).Example:100, 27, 34, 54, 59, 18, 52, 61, 78, 68, 82, 87, 85, 93, 91.Should now look like this …18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100.

4. Step 2 - Median • Find the median of your set of data*Remember the median is the value exactly in the middle of an ordered set of numbers*18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100. Q: What would you do it you had an even set of numbers?

5. Step 3 – Lower Quartile • Next, we consider only the values to the left of the median 18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100. We find the median of those numbers 18, 27, 34, 52, 54, 59, 61 Q: This number is call the lower quartile. Can you guess why?

6. Step 4 – Upper Quartile • Next, we consider only the values to the right of the median 18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100. We find the median of those numbers 78, 82, 85, 87, 91, 93, 100. Q: This number is call the upper quartile. Can you guess why?

7. Step 5 – Highest/Lowest Values • Now indicate your lowest and highest values 18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100.

8. Step 6 - Drawing • Now we are ready to begin to draw our graph. 18, 27, 34, 52, 54, 59, 61, 68, 78, 82, 85, 87, 91, 93, 100. Plot the lowest value, lower quartile, median, upper quartile, and the highest value on a number line.

9. Put a line through the Lower Quartile, Median, and Upper Quartile. Then Put a box around those lines

10. Lastly draw a line from your extreme values to the box There is your Box and Whisker Plot Q: Can you guess where the graph gets it’s name?

11. Time for a challenge activity