The following data are the number of pages in 40 books on a shelf. Press TRACE and use the arrow keys to examine the box plot. Press ENTER.Īrrow down to Freq: Press ALPHA. Use the down and up arrow keys to scroll.Īrrow down and then use the right arrow key to go to the fifth picture, which is the box plot. If you need to clear the list, arrow up to the name L1, press CLEAR, and then arrow down. To find the minimum, maximum, and quartiles:Įnter data into the list editor (Pres STAT 1:EDIT). The middle 50 percent (middle half) of the data has a range of 5.5 inches.The interval 59–65 has more than 25 percent of the data, so it has more data in it than the interval 66–70, which has 25 percent of the data.Range = maximum value – minimum value = 77 – 59 = 18.So, the second quarter has the smallest spread, and the fourth quarter has the largest spread. The spreads of the four quarters are 64.5 – 59 = 5.5 (first quarter), 66 – 64.5 = 1.5 (second quarter), 70 – 66 = 4 (third quarter), and 77 – 70 = 7 (fourth quarter).Each quarter has approximately 25 percent of the data.Calculator instructions for finding the five number summary follow this example: Otherwise, the box plot may not be useful. It is important to start a box plot with a scaled number line. The two whiskers extend from the first quartile to the smallest value and from the third quartile to the largest value. See the calculator instructions on the TI website or in the appendix. The following image shows the constructed box plot. The smallest value is one, and the largest value is 11.5. ![]() The first quartile is two, the median is seven, and the third quartile is nine. In those cases, the whiskers are not extending to the minimum and maximum values.ġ, 1, 2, 2, 4, 6, 6.8, 7.2, 8, 8.3, 9, 10, 10, 11.5 You may encounter box-and-whisker plots that have dots marking outlier values. The box plot gives a good, quick picture of the data. Unless the median, first quartile, and third quartile are the same value, the median will lie inside the box or between the first and third quartiles. A box plot easily shows the range of a data set, which is the difference between the largest and smallest data values (or the difference between the maximum and minimum). The whiskers extend from the ends of the box to the smallest and largest data values. Approximately the middle 50 percent of the data fall inside the box. The first quartile marks one end of the box, and the third quartile marks the other end of the box. ![]() The smallest and largest data values label the endpoints of the axis. To construct a box plot, use a horizontal or vertical number line and a rectangular box. We use these values to compare how close other data values are to them. ![]() As mentioned previously, a box plot is constructed from five values: the minimum value, the first quartile, the median, the third quartile, and the maximum value. They also show how far the extreme values are from most of the data. Box plots, also called box-and-whisker plots or box-whisker plots, give a good graphical image of the concentration of the data.
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