How it works
This box and whisker plot quiz has 31 questions in three sets: read the five numbers off a plot, find the median and quartiles of a list, and work out the range, interquartile range and outliers.
Read the full guide
Three sets
The box and whisker plot multiple choice questions come in three sets. Read a box plot describes a plot in words and asks for its median, a quartile, the range or the share of the data in one section. Median and quartiles of a list gives five to eleven numbers. Range, IQR and outliers ends with the 1.5 × IQR rule.
How the quartiles are found
Q1 is the lower half's median in the ordered list and Q3 the median of the upper half. When the count is odd, the middle value is left out of both halves.
- Order the list first. The median of 12, 7, 15, 9, 20 is 12, not 15.
- Each whisker and each part of the box holds about a quarter of the values, however long it is drawn.
- Outlier fences: Q1 − 1.5 × IQR and Q3 + 1.5 × IQR.
Questions and answers
What is the five-number summary?
The minimum, the first quartile (Q1), the median, the third quartile (Q3) and the maximum, in that order. A box plot draws all five: the two whisker ends, the two edges of the box and the line inside it.
How do you find the interquartile range?
Subtract the first quartile from the third: IQR = Q3 − Q1. On a box plot it is the length of the box. For Q1 = 12 and Q3 = 27 the interquartile range is 15.
How do you find outliers on a box and whisker plot?
Multiply the interquartile range by 1.5. A value more than that distance below Q1 or above Q3 is an outlier. With Q1 = 10 and Q3 = 18, anything below −2 or above 30 is one.
Do you include the median when finding quartiles?
This quiz leaves the middle value out of both halves when the count is odd. Some textbooks include it in both halves, which can give a different quartile, so use the method your class uses.