Surgeon Outcomes – Funnel Plot Key

The two “funnel” plots on each page show the Trust’s and surgeons’ 90-day mortality after planned surgery for bowel cancer. The Trust and surgeons will appear as red dots with all other results seen as blue dots for comparison. Placing the cursor over a red dot will reveal the Trust or surgeon’s name and outcome data.


The dots show the result for an individual NHS Trust or surgeon.

  • a RED dot indicates the outcome for this Trust and surgeons working at the Trust
  • a BLUE dot indicates the outcomes for all other Trust and surgeons

Vertical axis

Vertical axis (y axis) is the adjusted 90-day postoperative mortality (%).
Dots higher up the funnel plot indicate a higher mortality rate.

Horizontal axis

Horizontal axis (x axis) is the number of operations (volume) performed at a Trust or by a surgeon.
Dots to the right of the funnel plot indicate more procedures performed.


The green zone shows the range of mortality that could be explained by random variation. A Trust or surgeon within this zone has a mortality rate in the expected range that can be explained by random variation alone. The zone is funnel shaped because outcomes at low volumes are more affected by random variation (giving a larger acceptable range) than at high volumes when random variation has less effect.

A Trust or surgeon in the pink zone above the funnel limit is identified as a negative “outlier”. This means that the Trust/surgeon have been asked to check the accuracy of their data and examine what might have caused the higher than expected rate. A Trust or surgeon in the lower pink zone is a positive “outlier” with a mortality rate better than expected when compared to the national average.