Model | Predictor | R^{2}
| R^{2}change | Standardised β | P values | Mean |

1 | Demographics | 0.017 | 0.017 | <0.001 | ||

Gender | 0.009 | 0.766 | ||||

Age | −0.067 | <0.001 | ||||

Experience | 0.141 | <0.001 | ||||

2 | Site | 0.030 | 0.013 | 0.134 | <0.001 | |

3 | Phase | 0.037 | 0.006 | 0.067 | <0.001 | |

4 | Independent observers | 0.129 | 0.092 | −0.35 | <0.001 | 4.90* |

5 | Nurse | 0.134 | 0.005 | 0.086 | <0.001 | 5.94† |

6 | Surgeon | 0.134 | 0.001 | 0.029 | 0.028 | 5.70† |

6 | Anaesthetic assistant | 0.000 | Excluded | 0.720 | 5.63† | |

6 | Anaesthetist | 0.000 | Excluded | 0.720 | 5.54† | |

All clinical roles | 0.006 | <0.001 | 5.75† |

Mean domain ratings by independent observer and clinical role are shown in the right hand column.

*Independent Observer Mean score.

†Mean is significantly different compared with the Independent Observers’ mean score for the matched cases. Mean score is Bonferroni adjusted (p<0.001).

*Note*: Column 1: sequential steps for models in regression analysis. Column 2: predictors of the WHOBARS scores. Column 3: R^{2}=multiple correlation coefficient squared reflecting sum of variances explained by current and all previous models (steps) above. Column 4: R^{2}change, reflecting variance uniquely explained by the current model. Column 5: Standardised β=beta coefficient reflects how change of the predictor variable (demographics and so on) influences the outcome for the dependent variable in SD units (where there are multiple predictors, eg, Site and Phase, the largest β values are included). Column 6: p<0.05 indicates statistically significant effect. Column 7: mean rating scores.