Box And Whiskers Plot

Definition of Box and Whiskers Plot

Box plot means a figure or diagram which gives an optical delegacy to data’s distribution, highlighting the point where maximum values are lying & the lying values which differ greatly from those average values are called as outliers. We can also call box plots as a box and whisker-diagram or we can also call it as a box and whisker plot.

Box and whisker plot is said to be descriptive-measure’s pictorial or graphic combination. It transmits more data in comparison to the error-bar plot by using five numbers. These numbers are listed below:

• (Q1) Lower Quartile
• (Q2) Median
• (Q3) Upper Quartile
• Smallest values
• (Range) Largest-values

Let us take following set of data for explaining above numbers: 10, 22, 29, 33, 34, 37, 42, 42, 48, and 50. In the above data the five calculated numbers are as follows:

• (Q1) Lower Quartile = 22
• (Q2) Median = 34
• (Q3) Upper Quartile = 42
• Smallest values
• (Range) Largest-values = 10 & 50

Quartiles

We can split an arranged data-set into four quarters. The 1^st split, median, creates 2 halves and we can subdivide each ½ further for giving quarters, splits actually are medians for every ½.

The quartiles have been termed as hinges & it marks the box’s end. The whiskers extend from hinges towards extremes. Inside the above box, median’s position has been marked. The diagram has been drawn based on the data-set mentioned above. The plot drawn is asymmetrical and median also isn’t in box’s centre & whiskers too are not if equal-length. From, the above diagram it is indicated that skewed distribution is towards left.

Box and whiskers plot not only shows 4 splits but also from it we can make out the direction towards which data is swaying. Basically, from this plot we get a sound data’s distribution overview.

Box and Whisker Plot’s elements

The elements of box and whisker plots are mentioned below:

• Box’s side lying at the bottom represents 1^st or lower quartile & upper side called as 3^rd quartile. Thus, the perpendicular central-box’s width represents inter-quartile deviation.
• The line drawn horizontally within the box has been termed as median.
• The perpendicular lines popping out of the box stretches to data-set’s minimum values & maximum values, till the difference in between the median and the values is not greater by 1 and ½ times from inter quartile-range. By 2 short horizontal-lines mark the whisker’s ends.
• Values which are plotted beneath the bottom-whisker & above the whisker lying at top are regarded as outliers.