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How to Read and Interpret a Box and Whisker Plot in Tableau




How to read a box plot inteller in this example I have a disaggregated box plot by region and category so for each unique region category I have a box plot with each possible record as a point the hover over the Box pot you’re going to see some information the median which is right here above the dark gray is 142.2 so the 50th percentile is 142. If you go down to the bottom of the gray this is going to be the 25th percentile which is also called the lower hinge so that’s 47. So the 25th percentile on this category is 47. If you move up to the top of the box plot the top of the gray you get 328 which is the upper hinge or the 75th percentile within this category As you move up there’s a line at the top called the upper whisker I’m going to Define what that is and how you calculate it the upper whisker is at 7 22. The upper whisker is what’s used to define outliers anything above this line is called an outlier so all these points on top are called outliers because you’re going to take 1.5 times this range so take the range of the dark gray and the light gray multiply it by 1.5 so this would be about one this gets to about point one and a half of that range and you get the upper whisker the same thing happens at the bottom to get the lower whisker but it’s already at zero so it’s not going any further down than zero again anything above the whisker is an outlier the reason we look at the data like this is to compare groups you can see that the median within this group is much higher than the median within this group even the 75th percentile is less than the median in the first group and you compare medians percentiles outliers between all the groups in a quick and easy way one point to make within a tableau box plot is these are not exact values what Tableau does is finds the closest Mark that is closest to the value closest to the median closest to the 75th percentile closest to the upper whisker and it dwells a line there so if you’re doing statistics and you find that this upper whisker is not the exact value that it should be that’s probably true that low is just looking for a place to draw the line a box plot can be edited as well by right clicking selecting edit and you have some formatting options and you can decide to extend the whiskers all the way to the end of the data instead and that’s a box plot in Tableau hope this helps

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