Finding outliers with QUARTILE and the IQR rule
Finds Q1, the value 25% of the way up the data. Use 3 for Q3. IQR = Q3 - Q1. A value more than 1.5 times the IQR below Q1 or above Q3 is flagged as an outlier.
Understanding Finding outliers with QUARTILE and the IQR rule in ACARA Digital Technologies Years 9–10
What it does: If D2 holds Q1 and D4 holds the IQR, then Q1 - 1.5*IQR gives the lower fence. IF with OR checks both fences (F2 lower, G2 upper) and labels the value an outlier if either test is true. The last number is the quartile number: 1 gives Q1, 2 gives the median and 3 gives Q3. It is not a percentage. Use 3 for Q3, the value 75% of the way up the data. IQR = Q3 - Q1. It is the spread of the middle 50% of the data, so you subtract. The lower fence is Q1 - 1.5 x IQR. Check that you use the IQR cell (E3), not the Q3 cell (E2).
Common mistakes: Quart 2 returns the median, not Q3. Q3 needs quart 3, so the line should be =QUARTILE.INC(B2:B100,3). QUARTILE.INC needs a second argument saying which quartile to find. For Q1 it should be =QUARTILE.INC(B2:B100,1).
Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.
This module's key terms are also in a printable crossword (Modules 378–412) and word search (Modules 333–412).
Take this worksheet further — free with Cloodit
Each concept is reinforced from every angle — learned, then applied, then tested.
Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.
Over 100 of them, across seven natural biomes.
Turns their work into revision material ready for Flash Cards and Exam study.
Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.
Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.
Quick Questions
Match the Pairs
Key Term
=QUARTILE.INC(B2:B100,1)Fill in the Blanks
Spot the Error
Student with a class code? Join your class →