Box plots are useful for comparing different groups. Here are two sets of plots that show the weights of some berries and some grapes.
![A box plot and dot plot for “berry weights in grams.” The numbers 1 through 8 are indicated. The box plot is above the dot plot. The five-number summary for the box plot are as follows: Minimum value, 2. Maximum value, 6.5. Q1, 2.5. Q2, 3.5. Q3, 4. The data for the dot plot are as follows: 2 grams, 2 dots. 2.5 grams, 3 dots. 3 grams, 4 dots. 3.5 grams, 4 dots. 4 grams, 2 dots. 4.5 grams, 2 dots. 5.5 grams, 1 dot. 6.5 grams, 1 dot.](https://cdn.openupresources.org/uploads/pictures/6/6.8.19.Images.student.summary.01.png)
![A box plot and dot plot for “grape weights in grams.” The numbers 1 through 8 are indicated. The box plot is above the dot plot. The five-number summary for the box plot is as follows: Minimum value, 3. Maximum value, 9. Q1, 4.5. Q2, 5. Q3, 6. The data for the dot plot are as follows: 3 grams, 1 dot. 3.5 grams, 2 dots. 4 grams, 2 dots. 4.5 grams, 4 dots. 5 grams, 4 dots. 5.5 grams, 4 dots. 6 grams, 3 dots. 6.5 grams, 3 dots. 7 grams, 1 dot.](https://cdn.openupresources.org/uploads/pictures/6/6.8.19.Images.student.summary.02.png)
Notice that the median berry weight is 3.5 grams and the median grape weight is 5 grams. In both cases, the IQR is 1.5 grams. Because the grapes in this group have a higher median weight than the berries, we can say a grape in the group is typically heavier than a berry. Because both groups have the same IQR, we can say that they have a similar variability in their weights.
These box plots represent the length data for a collection ladybugs and a collection of beetles.
![Two sets of box plots for "lengths in millimeters". The numbers 4 through 16 are indicated in increments of 2. There are tick marks midway between the indicated numbers. The top box plot is for "ladybugs". The five-number summary is as follows: Minimum value, 6. Maximum value, 10.5. Q1, 8.5. Q2, 9. Q3, 10. The bottom box plot is for "beetles". The five-number summary is as follows: Minimum value, 5. Maximum value, 15.5. Q1, 7.5. Q2, 9. Q3, 13.5.](https://cdn.openupresources.org/uploads/pictures/6/6.8.19.Images.student.summary.03.png)
The medians of the two collections are the same, but the IQR of the ladybugs is much smaller. This tells us that a typical ladybug length is similar to a typical beetle length, but the ladybugs are more alike in their length than the beetles are in their length.