We could simply align two different box plots and then compare the vital data from each to see any differences in the information.
Using box plots we can compare data without even having to plot the cumulative frequency graph. This means that, from one box plot, we have been told all the main data that is shown in a cumulative frequency graph.
#Semi interquartile range full
The ‘whiskers’ on the plot are the red lines that extend horizontally and show the full range of the data from the lowest value to the highest. This box plot has essentially been drawn by extending the lines we create for the lower quartile, median and upper quartile. The example below uses the same curve seen earlier in this section with a box plot added. This information will allow us to draw conclusions from the data and is all very easy to spot from the box plot. The box plot is often drawn beneath the graph and will display the range of the data, the upper and lower quartiles (as well as the interquartile range) and the median. Box plotsĪ box plot (sometimes known as a box and whisker plot) is a very useful tool when working with cumulative frequency graphs. If the ranges are large, the data is less accurate. If the ranges are small, the data is more accurate. This then gives us an idea of the data accuracy. If the range is large then the values vary a lot more than a data set with a smaller range. The ranges will then tell us of the spread of the data. The interquartile range then gives us the middle 50% so we have data that is much more accurate as it is better to compare the interquartile ranges of two data sets. The best use of an interquartile range is to disregard any very high and very low values which may have occurred due to inaccuracy in testing. Two data sets may have the same mean, median and mode but different ranges. And the semi-interquartile range is half of this which is 7. Find the interquartile range and semi-interquartile range.įor the interquartile range we must take the lower quartile from the upper to give: You are told that the lower quartile for a data set is 38 and the upper quartile is 52.
#Semi interquartile range how to
The names of these two ranges do sound rather complicated but really they are quite straightforward and are defined as:īy using these two equations we can find values for the interquartile range and semi-interquartile range easily by just using the values for upper and lower quartile that we already know how to work out.
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