Copyright © Ed2Net Learning, Inc.1 Box-and-Whisker Plots Grade 7 Pre-Algebra

Copyright © Ed2Net Learning, Inc.2 Making Box-and-Whisker Plots  A box-and-whisker plot displays the distribution of data items along a number line.  Quartiles divide the data into four equal parts. whisker box Least value Lower quartile Median (middle quartile) Upper quartile Greatest value

Copyright © Ed2Net Learning, Inc.3 Example  The table shows Unites States crops harvested from 1988 to Make a box-and- whisker plot. YearAcres (millions) YearAcres (millions)

Copyright © Ed2Net Learning, Inc.4 Example  Step 1: Arrange the data in order from least to greatest. Find the median.  298, 308, 314, 317, 318, 318, 321, 322, 323, 326, 326, 327, 333  Step 2: Find the lower quartile and upper quartile, which are the medians of the lower and upper “halves”  298, 308, 314, 317, 318, 318, 321, 322, 323, 326, 326, 327, 333  Lower quartile = = 631 =  Upper quartile = = 652 = 326 2

Copyright © Ed2Net Learning, Inc.5 Example  Step 3 Draw a number line. Mark the least and greatest values, the median, and the quartiles. Draw a box from the first to the third quartiles. Mark the median with a vertical segment. Draw whiskers from the box to the least and greatest values

Copyright © Ed2Net Learning, Inc.6 Your Turn!  Draw a box-and-whisker plot for the distances of migration of birds (thousands of miles): 5, 2.5, 6, 8, 9, 2, 1, 4, 6.2, 18.7.

Copyright © Ed2Net Learning, Inc.7 Compare Data  Example 2: Use box-and-whisker plots to compare orca whale masses and hippopotamus masses.  Orca whale masses (kg)  3,900; 2,750; 2,600; 3,100; 4,200; 2,600; 3,700; 3,000; 2,200  Hippopotamus masses (kg)  1,800; 2,000; 3,000; 2,500; 3,600; 2,700; 1,900; 3,100; 2,300 Draw a number line for both sets of data. Use the range of data points to choose a scale. 1,000 2,000 3,000 4,000 5,000 Orca whale Hippopotamus

Copyright © Ed2Net Learning, Inc.8 Your Turn!  Compare annual video sales and CD sales by making two box-and-whisker plots below one number line.  Videos (millions of units): 28, 24, 15, 21, 22, 16, 22, 30, 24, 17  CDs (millions of units): 16, 17, 22, 16, 18, 24, 15, 16, 25, 18

Copyright © Ed2Net Learning, Inc.9 Analyzing Box-and-Whisker Plots  Example: Describe the data in the box-and- whisker plot The highest score is 90 and the lowest is 50. At least half of the scores are within 10 points of the median, 75.

Copyright © Ed2Net Learning, Inc.10 Your Turn!  Describe the data in the box-and-whisker plot

Copyright © Ed2Net Learning, Inc.11 Analyzing Box-and-Whisker Plots  Example: The plots below compare the percents of the voting-age population who said they registered to vote in U.S. elections to the percents who said they voted. Which conclusion best reflects the data collected? a) Percent voted was about 15 less than percent registered b) Percent voted was about half the percent registered c) Percent voted was equal to the percent registered d) Percent voted was about 15 more than percent registered voted registered The median of the percent who voted was about 50 and the median of the percent who registered was about 65: 65 – 50 = 15. The answer is A.

Copyright © Ed2Net Learning, Inc.12 Your Turn!  Use the box-and-whisker plots below. What conclusions can you draw about heights of Olympic basketball players? men women

Copyright © Ed2Net Learning, Inc.13 Stem-and-Leaf Plots  A stem-and-leaf plot organizes data by showing the items in order.  The leaf is the last digit to the right.  The stem is the remaining digit or digits. Stem  15.7  leaf Stem  32  leaf

Copyright © Ed2Net Learning, Inc.14 Example  Use the table to construct a stem-and- leaf plot. Then find the median, mode, and range. Broadway Productions SeasonNew Shows

Copyright © Ed2Net Learning, Inc.15 Example  Step 1: Choose the stems. For this data set, use the values in the tens place. Draw a line to the right of the stems.  Step 2: Leaves are single digits, so for this data set the leaves will be the values in the ones place. Stems   leaves

Copyright © Ed2Net Learning, Inc.16 Example  Step 3: Arrange the leaves on each stem from least to greatest. Include a title and a key that shows how to read your stem- and-leaf plot.  Since the data items are in order, the median is the midpoint. The median is the mean of the fourth and fifth values, or 37.  The mode corresponds to the most repeated leaf. The mode is 37.  The range is the difference of the greatest and least values, or means 28  key

Copyright © Ed2Net Learning, Inc.17 Your Turn!  Make a stem-and leaf plot for the set of data. Then find the median, mode and the range.  15, 22, 25, 10, 36, 15, 28, 35, 18

Copyright © Ed2Net Learning, Inc.18 Back-to-back stem-and-leaf plot  Draw a back-to-back stem-and-leaf plot for the winning times in the Olympic 100-m dash. Find each median and mode. Winning Times, 100-m Dash (seconds) YearMenWomen

Copyright © Ed2Net Learning, Inc.19 Example  Use seconds for the stem and tenths of seconds for the leaves. Put the leaves in ascending order starting at stem.  The median of the times for men is 10.0s. The median of the times for women is 11.0s. The modes of the times for men are 9.9s and 10.0s. The modes of the times for women are 11.0 s and 11.1s. Men’s Times Stem Women’s Times (tenths of second) (seconds) (tenths of second) means 10.0   means 10.5

Copyright © Ed2Net Learning, Inc.20 Your Turn!  Make a back-to-back stem-and-leaf plot for the pair of data sets. Then find the median and mode.  Set A: 9.1, 8.2, 7.3, 6.4, 7.3, 8.5  Set B: 7.6, 9.2, 8.2, 8.3, 9.7, 7.6

Copyright © Ed2Net Learning, Inc.21 Break!!!

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Copyright © Ed2Net Learning, Inc.23 Assessment 1. What are the highest and the lowest prices for the CD players? 2. What is the lower quartile price? 3. What is the median price? 4. What is the upper quartile price? 5. About half of the prices are within what amount of the median? Prices of Portable CD Players ($)

Copyright © Ed2Net Learning, Inc.24 Assessment 6. Which numbers are the stems? 7. What is the least time spent for each set of data? 8. What is the median for each set of data? 9. What is the mode for each set of data? 10. What is the range for each set of data? Class A Class B means 63   means 61 Time Spent on Homework (min)

Copyright © Ed2Net Learning, Inc.25 Good Job!  Remember to do the practice worksheets!!!