Two-way tables represent data that is classified by two criteria.
Right | Left | |
---|---|---|
Enjoys English | 4 | 9 |
Doesn't enjoy English | 2 | 15 |
To read a two-way table, look at the column and row that a number is in to find the right cell, the box where a single number is written. For example there are 9 students who are left-handed and enjoy English (top-right cell), and 2 students who are right handed that don't enjoy English (bottom-left cell). Tables will often include totals of each column, each row, and the total sum in the corner:
Right | Left | Total | |
---|---|---|---|
Enjoys English | 4 | 9 | 13 |
Doesn't enjoy English | 2 | 15 | 17 |
Total | 6 | 24 | 30 |
The categories should always be chosen so that each data point goes in exactly one of the cells.
This table describes the departures of trains out of a train station for the months of May and June.
Departed on time | Departed late | |
---|---|---|
May | 113 | 31 |
June | 108 | 33 |
How many trains departed during May and June?
What percentage of the trains in June were delayed? Write your answer as a percentage to one decimal place.
What fraction of the total number of trains during the 2 months were ones that departed on time in May?
Two-way tables represent data that is classified by two criteria.
A two-way table often presents information that could also be presented with a Venn diagram. We can convert between a two-way table and a Venn diagram by matching up their different parts.
The number that is in both chosen categories (4) goes in the overlap of the two circles.
The other value in the "Entered" row (9) represents the "Entered and right-handed" students, and goes in the "Entered" circle outside the overlap.
The other value in the "Left" column (2) represents the "Didn't enter and left-handed" students, and goes in the "Left-handed" circle outside the overlap.
Any cells that are in neither the highlighted row nor the highlighted column (15) goes into the surrounding box, outside both circles.
Students in Irene's class were asked if they owned a dog and asked if they owned a snake. The following two way table shows that information.
Owns a dog | Doesn't own a dog | |
---|---|---|
Owns a snake | 2 | 3 |
Doesn't own a snake | 13 | 11 |
Construct a Venn diagram that represents the information provided in the two-way table.
We can convert between a two-way table and a Venn diagram by matching up their different parts.