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A single number is not enough to understand the cancer burden in an area. As is always the case with statistical estimates, each estimate has a degree of uncertainty, or imprecision, around it. The larger the uncertainty associated with an estimate, the less convincing it is that this is the true value. Conversely, the smaller the uncertainty associated with an estimate, and the further away from the Australian average it is, the more likely it is to reflect a real difference. Areas with smaller populations are generally more likely to have wider uncertainty around them. The level of uncertainty is demonstrated in three ways.

V plots

In V plots, the y-axis shows the confidence or probability that the estimate is different to the Australian average. The x-axis shows the value of the estimate in relation to the Australian average. The Australian average is shown at 1 on the bottom axis. Dots to the left of the Australian average are lower, dots to the right of the Australian average are higher. There is greater certainty that the dots closer to the top of the graph are more likely to be real differences, while there is more uncertainty about the true value of the dots nearer to the bottom of the V plot (in the slightly lighter region).

As an example, the dot for Inverell for ‘all cancers combined’ is to the right of the Australian average, with a high probability (inside the darker shaded region) of being different to the Australian average. This suggests that we can confidently interpret this estimate as the diagnosis rate for this cancer is 8% higher than the Australian average and likely to be a real difference.

This interpretation is shown in the panel that pops up when you select an individual SA2 area on the map. The square for diagnoses of ‘all cancers combined’ is orange (meaning higher than the Australian average), with the text showing "8% above the Australian average, likely to be a real difference" under "All cancers".

Wave plot

The Wave plot indicates the level of uncertainty for the specific estimate for Inverell example. The small white circle in the centre shows the reported estimate, while the horizontal line shows the range in which we are fairly confident the true estimate lies. The height of the shaded curve, or wave, reflects the probability that the true estimate lies in that range.

Transparency

The transparency of the colours in the maps will show how confident we are that the differences are real differences (no transparency), rather than being due to chance (lots of transparency). The background colour of the maps is yellow (representing the Australian average). This means that if an estimate for an area has a lot of uncertainty about it, then we interpret that estimate as being no different to the Australian average.