Rare event charts are helpful when you know your data will not follow a normal distribution (for example, when measuring counts or wait times). The g-chart is an effective way to understand whether rare events are occurring more frequently than expected and warrant an intervention. A g-chart counts the number of possible opportunities since the last event. If you plot this type of data using a standard Shewhart control chart, you might see many more false signals, as the limits might be too narrow. The Adverse Reactions.jmp sample data table contains simulated data about adverse drug events (ADEs) reported by a group of hospital patients. An ADE is any type of injury or reaction the patient suffered after taking the drug. The date of the reaction and the number of days since the last reaction were recorded.