C4.1.15—Chi-squared test
Chi-squared test explains how ecological evidence links organisms, resources and interactions to population size, distribution or community structure in a habitat.
- Syllabus
- First assessment 2025
- Objective
- C4.1.15
- Level
- HL
Exam analysis
Chance of appearing4%of analysed past papers
Latest appearanceMay 2022
Most common paperPaper2
Typical marks1
Common command terms
- Identify
- Outline
- Determine
- Explain
- Calculate
- State
Scoring notes
- Common mistake
- Using non-random sampling when the estimate requires representative quadrat positions.
Recent exam appearances
May 2022Paper2 ["HL"] · TZ23(d)[ 1 ]C4.1.15—Chi-squared test
May 2022Paper2 ["HL"] · TZ23(c)[ 1 ]C4.1.15—Chi-squared test
May 2022Paper2 ["HL"] · TZ23(b)[ 1 ]C4.1.15—Chi-squared test
November 2020Paper1 ["HL"] · TZ014[ 1 ]C4.1.15—Chi-squared test
May 2018Paper3 ["HL"] · TZ21(b)[ 3 ]C4.1.15—Chi-squared test
Practice this objective
Coverage 2017–2022 · Updated 16 Jul 2026
Concept essentials
- Chi-squared test must be linked to the correct ecological unit, method or species interaction.
- The evidence for chi-squared test depends on measurable abundance, distribution, survival or resource patterns.
- Chi-squared test is clearest when cause, ecological process and population outcome are kept distinct.
- Field or graph evidence for chi-squared test needs biological interpretation, not values alone.