This 2x2 contingency table summarizes the joint distribution of Proton Event short-term warnings during the period 1987 through 2006. The "Correct Null" value in the table represents the number of days in the period for which no warning was issued and no proton event activity occurred. The summary statistics derived from the contingency table include the Bias (values less than 1 indicate fewer warnings issued than events observed), Heidke skill score (a corrected skill score that accounts for hits due to chance), Critical Success Index (also called the Threat Score), Probability of Detection (POD), and the False Alarm Ratio (FAR). Detailed definitions of these metrics are in the Verification Glossary.

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