Step 4: Epidemiology primers
Step 4 of 5
Before you start: a web browser. The R primers help but are not required. When you finish: you can compute a prevalence, a rate, a risk ratio and an odds ratio, and say what each one means.
2 short pages. They cover the arithmetic the lectures assume you already have.
Each page downloads about 17 MB to run R in your browser. If that fails, you lose nothing: every answer is printed in the text as well. You can follow both pages with a pencil and a calculator.
The 2 primers
6 · Measuring disease
Prevalence, risk, rate and person-time. Which question needs which. ~17 MB
7 · Measuring association
The 2×2 table. Risk ratio, odds ratio, risk difference, NNT (number needed to treat). ~17 MB
Do them in order. Primer 7 builds on Primer 6.
How to work through a primer
- Open the page. Wait for the cells to become ready.
- Press Run on every cell, from the top down.
- Change a number and run it again. Nothing is marked.
- If a cell will not run, read the printed answer and do the sum on paper.
You should see: output appear under each cell after you press Run.
If it does not work: the fixes are the same as for the R primers. Try a phone hotspot, or read the page as ordinary text.
These 2 pages are mostly reasoning, not code. The R in them is light on purpose.
Get the denominators right here and the rest of the week is much easier. Nearly every mistake with a risk ratio or an odds ratio is a mistake about what went underneath the line.
Step 4 is done
You have finished the primers.