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CPT Help Home -> Specific Menu Items -> Tools -> Verification -> ROC Graphs ROC GraphsThe ROC graphs are constructed using probabilistic retroactive forecasts. The ROC statistics are calculated using predictions for all gridpoints / stations / series. The probabilistic forecasts are binned to the nearest 10% (in accordance with the WMO's Standardized Verification System for Long-Range Forecasts - SVSLRF), although there is an option to bin to the nearest 5% (Options ~ Verification Settings). Results are shown separately for the three categories, and the areas beneath the graphs, calculated using the trapezium rule, are shown. Note that the ROC areas will not necessarily agree with the 2AFC scores for the individual categories shown on the Probabilistic Scores page because the areas are calculated using binned forecast probabilities, whereas the scores page shows scores for continuous probabilities.The ROC statistics can be saved by right-clicking on the graphs. In a similar manner the graphs themselves can be saved and the titles customised. The graphic can be saved as a BMP, EMF, GIF, JPEG, PCX, or PNG file by right-clicking anywhere in the child window. A default name is given to the graphic file, but this name can be changed using the browse button. The quality of the JPEG file can be adjusted using the slider or by the quality indicator, which ranges between 0.01 and 1.00. The highest quality is obtained using 1.00. The size of the JPEG file is affected by the quality chosen, with larger files being generated the higher the selected quality. The graphic title can be set using the Customise option upon right-clicking in the child window.
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