Quartis

How to use it

1. Dataset sorted: 5, 12, 18, 22, 28, 35, 42, 48, 55, 62 (n=10)
2. Q1 at position (10-1)×0.25+1 = 3.25: interpolate between 18 and 22
3. Q2 at position 5.5: average of 28 and 35
4. Q3 at position (10-1)×0.75+1 = 7.75: interpolate between 42 and 48

Common mistakes

• ⚠️ Using different quartile calculation methods inconsistently
• ⚠️ Not sorting data before calculating quartiles
• ⚠️ Confusing IQR with range (max-min)

Worked example

Calculate the quartiles Q1, Q2, Q3 and IQR for the dataset.

Quartiles divide data: Q1={q1}, Q2(median)={q2}, Q3={q3}, IQR={iqr}.

Input guide