The membership of a school club was categorized by grade level and whether each member participates in a school sport. The results are summarized in the table below.
| Grade level | Participates in a sport | Does not participate in a sport | Total |
|---|---|---|---|
| Junior | 18 | 12 | 30 |
| Senior | 15 | 15 | 30 |
| Total | 33 | 27 | 60 |
If one of the senior members is selected at random, what fraction of these members participates in a school sport?