Steve is a Clinical Director and Consultant in Intensive Care and Anaesthesia at Queen Alexandra Hospital, Portsmouth, UK. He is co-editor of the The Bottom Line and ICM Case Summaries. He also has developed and maintains the Wessex ICS and Portsmouth ICU sites. He is a Faculty Tutor for Intensive Care training and Council member of the Intensive Care Society. His interests include medical education, information technology and patient and relative experience. @stevemathieu75

Type 1 and 2 Errors

In statistical hypothesis testing, a type I error is the incorrect rejection of a true null hypothesis (a “false positive”), while a type II error is incorrectly retaining a false null hypothesis (a “false negative”). The more you try and avoid a Type I error (false positive), the more likely a Type II error (false negative) may happen. Researchers have found that an alpha level of 5% is a good balance between these two issues

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Fragility Index

Fragility Index is the minimum number of patients whose status would have to change from a “non-event” (not having the primary endpoint) to an “event” (having the primary end point) in order to turn a statistically significant result to a nonsignificant result. It is a simple metric to calculate and use.

Reporting the Fragility Index in RCTs may help readers make more informed decisions about the confidence warranted by RCT results

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