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Two-Way Tables

Two-Way Tables

Two-Way Tables contain data which contain data held by both row and column.

Entries will belong to two different sets. For example, students in a class are asked how they arrive at school. The data is shown by method of transport, and by boy/girl:

  Walk Car Bike Bus Train TOTAL
Girls 5 5 2 2 1 15
Boys 4 2 3 5 2 16
TOTAL 9 7 5 7 3 31

Each entry states membership of both sets: the number of girls arriving by bus is 2 out of the 31 students.

For the class as a whole, the most popular way to arrive is by walking (9 out of the total of 31).

But considering boys only, the most popular way to arrive is by bus (5 out of 16 boys). Make sure that you understand

Example 1

Students in a class are surveyed for how they arrive at school. The two-way table, above, shows the results.

How many students arrived by bike?

All students are being considered.

A total of 5 students arrive by bike.

Answer: 5

Example 2

Using the table, above, what, given a girl, is the least popular method of travelling to school?

Only girls are being considered.

Only 1 girl travels by train.

Answer: Train