Counts are rounded to whole people, so a fraction built from the counts can differ slightly in the third decimal from the exact formula in the readouts.
Set up the 2 × 2 table first, then compute. The worked solution builds line by line after a correct answer or when you ask for it.
Your jobEach round shows a 2 × 2 table with cells lit up, a formula or a short description. Filled cells are the numerator; outlined cells are the denominator. Name the measure as fast as you can. Keys 1 2 3 4 pick an answer. Three right in a row scores double.
Press Start to begin.
Fictional settings and practice numbers chosen to look realistic. They are not clinical reference values or advice.
Wrong picks are fine here. Each one tells you why.