IA idea · Health, biology & medicine
Do more doctors mean fewer infant deaths?
Research question
Across countries, how strongly is infant mortality related to the number of physicians per 1,000 people, and does the relationship remain after accounting for income?
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Why it makes a good exploration
Health systems decide where to spend money. Testing a simple relationship, then seeing how much of it is really about wealth, teaches careful statistical thinking.
The mathematics you'll need
- Scatter plots and logarithmic transformations
- Correlation and regression
- Controlling for a third variable by grouping
- Spearman's rank
The statistics, step by step
Worked with every number shown, with what examiners look for and the common mistakes: Spearman's rank correlation · Pearson's correlation and regression. Then run the same steps on your own data in Analyse my data, or start from the statistics workflow.
Where the data comes from
Infant mortality, physicians per 1,000 and GDP per capita from the World Bank.
- World Bank Open Data — Development indicators (GDP, life expectancy, mortality, internet use) for every country, usually from 1960.
- WHO Global Health Observatory — 1,000+ health indicators by country (immunisation, mortality, risk factors).
Real data for this idea
- Primary source: World Bank Open Data: Infant mortality rate (SP.DYN.IMRT.IN). Download the CSV and take one year for every country. Licence: CC BY 4.0 for most datasets (the World Bank's licence page lists any exceptions).
- Also useful: World Bank Open Data: Physicians per 1,000 people (SH.MED.PHYS.ZS). Match each country's latest value with infant mortality in the same year.
- Readable chart: Our World in Data: Infant mortality rate. Use it to see the pattern; download your numbers from the primary source or the chart's own download. Cite as: Our World in Data, ‘Infant mortality rate’, CC BY 4.0. Original source: United Nations Inter-agency Group for Child Mortality Estimation (2025).
Links checked October 2026; we link to the data and never copy it. More free data sets.
A possible outline
- Define the variables and years.
- Explore the raw relationship.
- Transform and model.
- Group by income and repeat.
- Reflect on confounding and data quality.
Pitfalls that cost marks
- Claiming causation.
- Mixing years across countries.
- Ignoring missing values.
Showing personal engagement
- Locate your own country.
- Investigate an outlier.
- Discuss policy implications carefully.
See Criterion C: personal engagement for what examiners look for.
Which course is it for?
| Course | Fit | Maths to lean on |
|---|---|---|
| AA SL | Good fit | Scatter plots and logarithmic transformations; Correlation and regression |
| AA HL | Not a natural fit | The mathematics is mainly from the AI course; at AA HL the exploration would need an AA-level approach (calculus, proof or probability theory) to reach the top of Criterion E. |
| AI SL | Good fit | Scatter plots and logarithmic transformations; Correlation and regression |
| AI HL | Fits, but add an HL technique | Scatter plots and logarithmic transformations; Correlation and regression |
Level: Accessible. A good first extended piece of maths, with room to go deeper. See how the IA differs between AA and AI, SL and HL.
How this idea reaches the top bands
Reflection (D)
For this idea, start with the weak points: claiming causation; and mixing years across countries. Say how each one affects your answer.
Use of mathematics (E)
SL: scatter plots and logarithmic transformations; correlation and regression; controlling for a third variable by grouping; spearman's rank, each explained in your own words and carried out correctly.
How health & biology explorations reach the top bands in general: Health, biology & medicine IA ideas. Guides: A · B · C · D · E · self-grade sheet.
Taking it further
Compare with nurses and midwives per 1,000 and discuss which matters more.
Extending it for HL
Add an HL technique the question genuinely needs: what an HL health & biology exploration adds.
See a complete IA, marked
Do students who sleep less react more slowly? (AI SL) is a complete health & biology exploration, marked on every criterion.
Frequently asked questions
Which IB Maths course is this IA idea for?
It works for AI SL, AI HL and AA SL. We rate it Accessible: a good first extended piece of maths, with room to go deeper.
What mathematics does this IA use?
Scatter plots and logarithmic transformations, correlation and regression, controlling for a third variable by grouping and spearman's rank.
Where can I get data for this IA?
Infant mortality, physicians per 1,000 and GDP per capita from the World Bank. Checked sources and tools: World Bank Open Data, Our World in Data and WHO Global Health Observatory.
Turn this idea into your IA
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