How fast did COVID-19 spread at the start? Comparing doubling times

AA SLAA HLAI SLAI HL Solid Also in: Modelling, Differential equations

Research question

What were the doubling times of confirmed COVID-19 cases in the first 30 days after the 100th case in [several countries], and how did they change after lockdown measures?

Adapt it: change the place, the data or the comparison until the question is yours.

Why it makes a good exploration

In spring 2020 the world learned about exponential growth the hard way. Fitting exponential models to the early data, and measuring how quickly growth slowed, is a powerful, well-sourced IA.

The mathematics you'll need

Exponential models and doubling time
Log-linear regression
Piecewise models before and after an intervention
Comparing rates between countries

Course labels show where a technique sits; using maths from outside your course is fine if you explain it clearly and say it is new to you.

Where the data comes from

Daily cumulative cases from the archived Johns Hopkins repository or Our World in Data.

Johns Hopkins CSSE COVID-19 repository (archived) — Daily cases and deaths by country, Jan 2020 – Mar 2023. No longer updated.
Our World in Data — Clean country-level time series (CO₂, population, health, energy, education) with CSV download on every chart.

Cite every source in a footnote where you use it and in your bibliography. Check the licence of any dataset you download.

A possible outline

Align countries by the day of the 100th case.
Fit exponential models to early data.
Compute doubling times.
Fit before/after intervention periods.
Reflect on testing rates and reporting delays.

Pitfalls that cost marks

Treating confirmed cases as infections.
Choosing intervention dates after seeing the data.
Ignoring weekend reporting dips.

Showing personal engagement

Include your own country and explain its timeline.
Compare with deaths, which are less affected by testing.
Explain doubling time to a younger student.

See Criterion C: personal engagement for what examiners look for.

Taking it further

Fit a logistic model and compare its predicted final size with what happened.

Turn this idea into your IA

Plan this IAOpens the planner with this question, the maths and data sources filled in. Desmos workspacePlot your data, fit models and keep your graphs with your plan. AI feedback on a draftCriterion-by-criterion feedback with evidence from your own text. Coaching, not rewriting. Examiner reviewPete, a practising IA examiner, reads your draft and talks it through with you (€100).