Chart characteristics (all charts)
| Type of chart | All charts (n=6287) n (%) |
| Quality and safety chart | 3003 (47.7) |
| Time series, between group or both | 6287 (100) |
| Time series only | 4741 (75.4) |
| Between group only | 640 (10.2) |
| Time series and between group | 906 (14.4) |
Further details available in online supplemental file 6.