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### Creating Box Plots

posted Mar 5, 2010, 2:43 PM by Prof Kiernan   [ updated Feb 6, 2014, 5:59 AM ]
 How to make a Box plot by hand: 1. Find the 5-number summary (smallest value, Q1, Median, Q3, & the largest value) 2. Construct a scale with values that include the minimum and maximum values 3. Construct a box extending from the first quartile to the third quartile and draw a line in the box at the median value 4. Draw lines extending outward from the box to the minimum and the maximum data values and you're done! How to make a Box Plot using the calculator:Put data into list #1: Press STAT Press ENTER (1:Edit) Put in variable under list 1 L1  Press ENTER (continue the last two steps until you have added all of the variables in your list)Get the 5 number summary: Press STAT Press CALC            Press 1 (1: 1-Var Stat)              Press 2nd             Press L1 (or the name of the list that you have put your information in)Press ENTERPress Down arrow (the last 5 things in the list are the 5 number summary)To see the Box Plot:Press 2nd Press Y=Press ENTERPress ENTERPress DOWN ARROW Press RIGHT ARROW (till you highlight the box plot with the dots)Press ENTERPress ZOOMPRESS 9 (9: zoom stat)Voila! You have your box plot!To find the Q1, Median, and Q3 by hand:Put your data in a list from small to largeFind the median (the value in the middle of the dataset) if there are 2 data values average them together to get the medianFind the first and second Quartiles (Q1 & Q3) the same way:make 2 separate data sets and  find the middle value of each new datasets.Find the Inter Quartile Range: Q3-Q1Apply the Interquartile range to the formula below to ensure there are no outliersIf there are outliers use the IQR (inter quartile range) to get the min and max values accepted as normal values Put any outliers on the plot as dots.