Conditional probability from a two-way table
Conditional probability from a two-way table.
- Identify the outcomes that are still possible after applying the condition.
- Use the number or probability meeting both requirements in the numerator.
- The denominator comes from the restricted sample space, not automatically the original total.
Example 1
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 8 | 5 | 13 |
| No club | 6 | 4 | 10 |
| Total | 14 | 9 | 23 |
Example 2
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 9 | 5 | 14 |
| No club | 7 | 4 | 11 |
| Total | 16 | 9 | 25 |
Your turn
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 10 | 5 | 15 |
| No club | 8 | 4 | 12 |
| Total | 18 | 9 | 27 |
Check answer
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 11 | 5 | 16 |
| No club | 9 | 4 | 13 |
| Total | 20 | 9 | 29 |
Check answer
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 12 | 6 | 18 |
| No club | 10 | 4 | 14 |
| Total | 22 | 10 | 32 |
Check answer
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 13 | 6 | 19 |
| No club | 11 | 4 | 15 |
| Total | 24 | 10 | 34 |
Check answer
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 14 | 6 | 20 |
| No club | 12 | 5 | 17 |
| Total | 26 | 11 | 37 |
Check answer
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 10 | 5 | 15 |
| No club | 8 | 4 | 12 |
| Total | 18 | 9 | 27 |
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 11 | 5 | 16 |
| No club | 9 | 4 | 13 |
| Total | 20 | 9 | 29 |
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 12 | 6 | 18 |
| No club | 10 | 4 | 14 |
| Total | 22 | 10 | 32 |
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 13 | 6 | 19 |
| No club | 11 | 4 | 15 |
| Total | 24 | 10 | 34 |
A pupil is selected at random. Given that the pupil takes the bus, find the probability they attend the club.
| Walk | Bus | Total | |
|---|---|---|---|
| Club | 14 | 6 | 20 |
| No club | 12 | 5 | 17 |
| Total | 26 | 11 | 37 |