A Box and Whisker Plot (or Box Plot) is a convenient way of visually displaying the data distribution through their quartiles. The lines extending parallel from the boxes are known as the “whiskers”, which are used to indicate variability outside the upper and lower quartiles.
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How do you read a Boxplot with whiskers?
At the ends of the box, you” find the first quartile (the 25% mark) and the third quartile (the 75% mark). The far left of the chart (at the end of the left “whisker”) is the minimum (the smallest number in the set) and the far right is the maximum (the largest number in the set).
Where do you find whiskers on a box plot?
The whiskers are the two lines outside the box, that go from the minimum to the lower quartile (the start of the box) and then from the upper quartile (the end of the box) to the maximum.
What is upper and lower whisker?
To understand box-and-whisker plots, you have to understand medians and quartiles of a data set. The lower quartile ( Q1 ) is the median of the lower half, and the upper quartile ( Q3 ) is the median of the upper half.
How far do the whiskers extend?
The “whiskers” extend from the ends of the box to the smallest and largest data values. The median or second quartile can be between the first and third quartiles, or it can be one, or the other, or both. The box plot gives a good, quick picture of the data.
How do you count whiskers?
The length of the upper whisker is the largest value that is no greater than the third quartile plus 1.5 times the interquartile range. In this case, the third quartile plus 1.5 times IQR is 10 + 1.5*6 = 19. The largest value that is no greater than 19 is 13, so the upper whisker will reach to 13.
What is the lower whisker?
Similarly, the lower whisker boundary of the box plot is the smallest data value that is within 1.5 IQR below the first quartile.
What does the line inside the box show?
The box length gives an indication of the sample variability and the line across the box shows where the sample is centred. The position of the box in its whiskers and the position of the line in the box also tells us whether the sample is symmetric or skewed, either to the right or left.
What is box and whiskers in math?
A box and whisker plot—also called a box plot—displays the five-number summary of a set of data. The five-number summary is the minimum, first quartile, median, third quartile, and maximum.A vertical line goes through the box at the median. The whiskers go from each quartile to the minimum or maximum.
How do you draw a box and whisker diagram?
Start by plotting points over the number line at the lower and upper extremes, the median, and the lower and upper quartiles. Next, construct two vertical lines through the upper and lower quartiles, and then constructing a rectangular box that encloses the median value point.
How do you make a box and whisker plot on word?
Create a box and whisker chart
- On the Insert tab, in the Illustrations group, click Chart.
- In the Insert Chart dialog box, on the All Charts tab, click Box & Whisker.
What is the upper bound for the whiskers?
The highest point of the upper whisker is the called the upper limit. The upper limit value equals Q3 + 1.5 * (Q3-Q1). Outliers are points that fall outside the limits of the whiskers. These are normally recognized as asterisks and are points that are greater than 1.5x the interquartile distance from each quartile.
How do you describe the spread of a box plot?
If you are interested in the spread of all the data, it is represented on a boxplot by the horizontal distance between the smallest value and the largest value, including any outliers. In the boxplot above, data values range from about 0 (the smallest non-outlier) to about 16 (the largest outlier), so the range is 16.
How do I find the upper quartile?
The upper quartile is the median of the upper half of a data set. This is located by dividing the data set with the median and then dividing the upper half that remains with the median again, this median of the upper half being the upper quartile.