This deep dive covers Special Cases and Outliers within Box Plots for GCSE Mathematics. Revise Box Plots in Statistics for GCSE Mathematics with 18 exam-style questions and 20 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 9 of 10 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 9 of 10
Practice
18 questions
Recall
20 flashcards
Special Cases and Outliers
Identifying Outliers
An outlier is typically defined as a value that is:
- More than 1.5 × IQR below Q1
- More than 1.5 × IQR above Q3
Example: If Q1 = 20, Q3 = 40, then IQR = 20
Lower fence: 20 - (1.5 × 20) = 20 - 30 = -10
Upper fence: 40 + (1.5 × 20) = 40 + 30 = 70
Outliers: Any values below -10 or above 70
Lower fence: 20 - (1.5 × 20) = 20 - 30 = -10
Upper fence: 40 + (1.5 × 20) = 40 + 30 = 70
Outliers: Any values below -10 or above 70
Modified Box Plots
When outliers are present:
- Calculate outlier boundaries
- Draw whiskers to the last non-outlier values
- Plot outliers as separate points