Topic explanation

Standard explanation

Mark n/4 on the CF axis, go across to the curve, down to x: that x is Q1. Median uses n/2. Q3 uses 3n/4. IQR = Q3 - Q1.

Key points

• n/4, n/2, 3n/4
• running total
• ogive vs upper boundaries
• keep the ideas separate
• Ogive Readings: Mark n/4 on the CF axis, go across to the curve, down to x: that x is Q1. Median uses n/2. Q3 uses 3
• WHAT — OGIVE READINGS: Mark n/4 on the CF axis, go across to the curve, down to x: that x is Q1. Median uses n/2. Q3 uses 3
• HOW — Use the idea: Identify what is given, select this topic's rule or evidence, apply it one step at a time, and check
• CORE UNDERSTANDING: Mark n/4 on the CF axis, go across to the curve, down to x: that x is Q1. Median uses n/2. Q3 uses 3

Labelled diagram