Models are a tool to combine data (what we know) with assumptions and theory (what we think) to learn about what we don’t know.

Example: January 2020

Can COVID-19 be controlled by contact tracing?

Example: January 2020

Can COVID-19 be controlled by contact tracing?

Hellewell et al., Lancet Glob Health, 2020

Probability of control vs. tracing effort

Probability of control depends on intensity of transmission and contact tracing effort.

Hellewell et al., Lancet Glob Health, 2020

We illustrate the potential impact that flawed model inferences can have on public health policy with the model described […] by Joel Hellewell and colleagues, which is part of the scientific evidence informing the UK Government’s response to COVID-19.

Gudrasani & Ziauddeen, Lancet Glob Health, 2020

“All models are wrong, but some are useful”

George Box

“All models are wrong, but some are useful”

• wrong: how wrong?
• some: which ones?