Risk Ranger calculates a (relative) risk ranking on the basis of a description of food contamination with pathogens. The "Risk Ranking" value is a simplified measure of relative risk of hazardous effects of microbiological agents, as can be read at the end of this page. It originates from the Australia's food safety information portal but today the site lacks references to it. To calculate the rank, a computer tool was developed. The tool is called "Risk Ranger: A Simple Food Safety Risk Calculation Tool". FAO supports this tool and provides you with an example for which the tool was used to evaluate the quality of fish. The various questions addressed in the tool are explained in detail in that example, and how different choises might affect the outcome. So, this example can help you if you consider to use the Risk Ranger tool.
The RiskRanger tool is compared by EFSA with different other tools for a similar type of assessment. The results of that evaluation are published in a Scientific Opinion of 2014. It shows that the relative ranking of (simulated) cases of a microbiological contamination of some foodstuffs as calculated by the different tools is quite similar, so it can be concluded that RiskRanger is fit for purpose.
The original tool is implemented in a (Microsoft Excel) spreadsheet that can be downloaded from the Internet for free. This spreadsheet is however to be controlled by macros, which are nowadays being considered unsafe and therefore mostly locked. Unlocking can be quite tedious. It was therefore decided to provide this portal with an online tool that fully mimics the spreadsheet, leading to results identical to the spreadsheet. The name of the online tool is kept "Risk Ranger".
To explain the approach that is being used by RiskRanger, the following text was taken from the spreadsheet: