Modified Boxplot vs Boxplot

Both terms below come up in the same part of the course, and students mix them up. Here is each one defined on its own, side by side, so you can see where they part company.

Modified boxplot

Describing data

A modified boxplot plots outliers as separate points and draws each whisker only to the most extreme value still inside the IQR fences.

A modified boxplot is the version you normally draw, because it shows outliers instead of burying them at the end of a long whisker. You first set the fences at Q11.5×IQRQ_1 - 1.5 \times \text{IQR} and Q3+1.5×IQRQ_3 + 1.5 \times \text{IQR}, where Q1Q_1 is the first quartile and Q3Q_3 is the third quartile, taking both by the median-excluded (TI-84) rule this site uses, then mark every value beyond a fence with its own dot. Suppose Q1=20Q_1 = 20 and Q3=32Q_3 = 32, so the IQR is 12 and the fences sit at 2018=220 - 18 = 2 and 32+18=5032 + 18 = 50: a value of 61 becomes a plotted point, and the upper whisker stops at the largest value at or below 50. The box is unchanged either way, still running from Q1Q_1 to Q3Q_3 with the median marked inside it.

Full entry for modified boxplot

Boxplot

Graphs and displays

A boxplot is a graph of the five-number summary, with a box from Q1 to Q3, a line at the median, and whiskers to the extremes.

A boxplot turns the five-number summary into a picture: a box spans Q1Q_1 (the first quartile) to Q3Q_3 (the third quartile), a line inside marks the median, and whiskers reach the smallest and largest non-outlier values. For example, a longer right whisker signals a right-skewed distribution. Points more than 1.5×IQR1.5 \times \text{IQR} beyond the nearer quartile are drawn separately as outliers. Boxplots make it easy to compare center and spread across several groups side by side.

Full entry for boxplot

Where each one fits in the course