Read a conditional fraction in a two-way table
The idea
A two-way table sorts the same observations by two categorical features.
Step by step
- A two-way table sorts the same observations by two categorical features.
- Identify the condition, such as among walkers; add just that row or column to find its total.
- Divide the count meeting both descriptions by the condition total, then simplify.
Example
A two-way table records travel and hats. Walk: 18 with a hat, 12 without a hat. Bus: 8 with a hat, 12 without a hat.
Among the students who walk, what fraction wear a hat?
Answer
The condition selects walkers only: 30 students. Of them, 18 wear hats, so the fraction is = 3/5.
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Make an invented two-way table about transport and hats. Compare the fraction among walkers with the fraction among all students.
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