The event rate refers to the frequency or proportion of individuals in a study or clinical trial who experience a specific event or outcome during a specified period of time.
The event rate is important because it helps to quantify the risk of an event occurring in a population under study. It is often expressed as a percentage or a proportion. For example if 48 out of 100 participants receive a blood transfusion, then the event rate is 0.48 or 48%.