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The Third (Upper) Quartile is the midpoint of the upper half of our data. Lower half of scores in Physics (in Bold): 30, 45, 68, 70, 78, 83, 85Ĥ2 and 45 are the first quartiles in Maths and Physics respectively (there is 1 data point both above and below) And the convention is to take our median out and have the sets that are left over. Now, lets take the median of each of those sets. And its essentially dividing our data into two sets. Lower half of scores in Maths (in Bold): 35, 42, 56, 66, 71, 78, 91 Now, when were trying to construct a box and whisker plot, the convention is, OK, we have our median. The First (Lower) Quartile is the midpoint of the lower half of our data. Ħ6 and 70 are the median values in Maths and Physics respectively (there are 3 data points both above and below these values). The median is the point at which there are an equal number of data points whose values lie above and below the median value. Now let us find the median, the first (lower) quartile and the third (upper) quartile These lines indicate variability outside the upper and lower quartiles, and any point outside those lines or whiskers is considered an outlier. The boxes may have lines extending vertically called whiskers. Scores in Maths: 35, 42, 56, 66, 71, 78, 91 A box and whisker chart shows distribution of data into quartiles, highlighting the mean and outliers. The box thus represents IQR (the inner quartile) in the diagrams of normal distributions above. A boxplot box always contains the 25th-75th percentile, the middle 50 of the population. To understand how a Box and Whisker chart is constructed, we have to first arrange our data in ascending order. The Box & Whisker chart displays the spread and skewness in a batch of data through its five-number summary: minimum, maximum, median, upper and lower quartiles. The meaning of a box in a boxplot can best be rembered by looking at the box turned on it side in the top half of the diagram. Ĭheck out live examples of Box and Whisker Chart in our charts gallery and JSFiddle gallery. The Box and Whisker consists of two parts—the main body called the Box and the thin vertical lines coming out of the Box called Whiskers. To find out unusual observations/errors in the data setīox and whisker plots are also very useful when large numbers of observations are involved and when two or more data sets are being compared.

The Box & Whisker chart displays the spread and skewness in a batch of data through its five-number summary: minimum, maximum, median, upper and lower quartiles.