Table 2 Summary statistics 2014–2017
|  | Overall mean ± SD | Between SD | Within SD | N (n) |
|---|---|---|---|---|
Characteristics ITCs | ||||
 Number of invasive treatments | 1571.85 ± 1881.56 | 1693.96 | 819.81 | 941 (338) |
 FTE physicians | 2.32 ± 2.45 | 2.35 | 1.04 | 941 (338) |
 FTE nurses | 1.49 ± 3.55 | 3.34 | 1.14 | 941 (338) |
 Number of locations | 2.61 ± 3.11 | 2.73 | 0.82 | 941 (338) |
 Chain membership | 0.40 ± 0.49 | 0.47 | 0.16 | 941 (338) |
 Non-profit providers | 0.68 ± 0.47 | 0.47 | 0.00 | 941 (338) |
Composite Quality indicators | ||||
 Reachable 24/7 | 0.67 ± 0.47 | 0.31 | 0.40 | 716 (313) |
 Personnel functioning system | 0.78 ± 0.41 | 0.38 | 0.21 | 716 (313) |
 Personnel malfunctioning system | 0.78 ± 0.41 | 0.36 | 0.22 | 716 (313) |
 Patient satisfactory questionnaire | 0.88 ± 0.33 | 0.32 | 0.16 | 716 (313) |
 ASA classification known | 0.48 ± 0.50 | 0.46 | 0.21 | 716 (313) |
 Screening delirium | 0.34 ± 0.48 | 0.42 | 0.23 | 716 (313) |
 Collaboration with (a) hospital(s) | 0.64 ± 0.48 | 0.45 | 0.20 | 716 (313) |
 Structural and process composite | −0.00 ± 3.31 | 3.19 | 1.48 | 716 (313) |
Quality outcomes | ||||
 Percentage infections | 0.28 ± 1.14 | 0.96 | 0.79 | 877 (318) |
 Percentage infections (> 0 postoperative infections & > =50 invasive treatments) | 0.47 ± 0.62 | 0.65 | 0.29 | 412 (189) |
 Average patient satisfaction score | 8.74 ± 1.17 | 0.40 | 1.12 | 19,338 (80) |
 Ratio promoters over total number of observations per provider | 0.52 ± 0.50 | 0.17 | 0.47 | 19,338 (80) |
 Ratio detractors over total number of observations per provider | 0.03 ± 0.17 | 0.04 | 0.17 | 19,338 (80) |
 Ratio 7 or more over total number of observations per provider | 0.95 ± 0.22 | 0.04 | 0.21 | 19,338 (80) |
 Ratio 8 or more over total number of observations per provider | 0.84 ± 0.36 | 0.09 | 0.35 | 19,338 (80) |
 Net Promoter Score (in ratio) | 0.55 ± 0.19 | 0.19 | 0.06 | 118 (55) |
Control variables | ||||
 Specialism ophthalmology | 0.23 ± 0.42 | 0.39 | 0.07 | 941 (338) |
 Specialism dermatology | 0.37 ± 0.48 | 0.47 | 0.13 | 941 (338) |
 Specialism orthopaedics | 0.11 ± 0.31 | 0.31 | 0.05 | 941 (338) |
 Specialism aesthetic surgery | 0.59 ± 0.49 | 0.47 | 0.18 | 941 (338) |
 Ratio ASA II over total number of patients | 0.13 ± 0.16 | 0.14 | 0.08 | 622 (241) |
 Ratio ASA III over total number of patients | 0.01 ± 0.06 | 0.04 | 0.04 | 623 (242) |
Robustness check | ||||
 Number of aesthetic invasive treatments | 502.40 ± 1269.82 | 972.17 | 844.36 | 488 (211) |
 Percentage infections after aesthetic surgery | 0.90 ± 6.81 | 7.76 | 4.16 | 449 (182) |