Boxand whiskerplotpowerpoint

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Boxand whiskerplotpowerpoint

  1. 1. Box & Whisker Plots SDAP 1.3 (Understand the meaning of, and be able to compute the minimum, the lower quartile, the median, the upper quartile, and the maximum of a data set).
  2. 2. Heat vs. Lakers 3/4/12 T. Murphy 0 points S. Blake 3 points A. Goudelock 7 points A. Bynum 16 points K. Bryant 33 points
  3. 3. Heat vs. Lakers 3/4/12 Minimum Value 0 First Quartile 3 Median 7 Third Quartile 16 Maximum Value 33
  4. 4. What is a box & whisker plot?  A box-and-whisker plot ◦ can be useful for handling many data values ◦ allow people to explore data and to draw informal conclusions when two or more variables are present ◦ show only certain statistics rather than all the data  Think back on the Lakers… did the box-and- whisker plot show rebounds? Fouls? Free throws?
  5. 5. Step One: Find the Median (middle)  The following numbers are the amount of marbles different boys own. 68 34 54 82 18 93 87 78 61 85 100 27 52 59 91 -------------------------------------------------------  To find the median, put the numbers in order & find the one in the exact middle 18 27 34 52 54 59 61 68 78 82 85 87 91 93 100
  6. 6. Step Two: The Lower Quartile  Focus only on the values to the left of the median: 18 27 34 52 54 59 61  Now we need to find the median of these numbers ◦ Since they’re already in order it’s easy to see the median of the values less than the median is 52  This value is called the “Lower Quartile” ◦ Think ahead: Using your knowledge of prefixes and suffixes, what does ‘quartile’ mean and how will knowing this help us design our box- and-whisker plot?
  7. 7. Step Three: The Lower Quartile  Now consider only the values to the right of the median: 78 82 85 87 91 93 100  You should have noticed the median of this set of numbers is 87  This value is called the “Upper Quartile”
  8. 8. Wait a minute… Too easy right?  What happens if you’re finding the median in an ordered set with an even number of values? ◦ You must first take the average of the two middle numbers.  For example: 3, 5, 7, and 10. Add the two middle numbers 5 + 7 = 12 Divide your answer by the number of values added 12 / 2 = 6 6 is the average and your median for this set.
  9. 9. Step Four: The Interquartile Range  You’re now ready to find the Interquartile Range (IQR).  The IQR is the difference between the upper quartile and the lower quartile.  In our case the IQR = 87 – 52 IQR = 35  The IQR is a very useful measurement because it is less influenced by extreme values, it limits the range to the middle 50% of the values.
  10. 10. Step Five: Draw Your Graph X
  11. 11. Now you try!
  12. 12. #1  What is the median of the set of data below? 34, 22, 18, 32, 26, 56, 49, 40, 34, 41, 12  34
  13. 13. #2  What is the upper quartile of the set of data below? 34, 22, 18, 32, 26, 56, 49, 40, 34, 41, 12  41
  14. 14. #3  What is the maximum value (upper extreme) of the set of data below? 34, 22, 18, 32, 26, 56, 49, 40, 34, 41, 12  56
  15. 15. DROPS ON A PENNY! partner activity  You will need: ◦ Cup of water ◦ Penny ◦ Paper towel ◦ Eye dropper ◦ 4 sticky notes ◦ Pencil
  16. 16. Directions  Working with a partner, take turns dropping one drop of water at a time on the penny.  Both partners count the drops as you go to assure for an accurate count.  When the water finally spills over the edge of the penny record on your sticky note how many drops you had before the water spilled  Each partner will take 2 turns  Be sure to dry the penny between turns  When your team is done, clean up and construct a box-and-whisker plot for your information. ◦ When everyone is finished we will make one for the class’ results!

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