Dr Henry Jefferson, Consultant Anaesthetist
#QuestionFeedback 4. Normal Distribution A useful reminder of the familiar 68–95–99.7 rule. For a normal distribution: • 68% of observations lie within ±1 SD • 95% within ±2 SD • 99.7% within ±3 SD Therefore, approximately 0.3% lie OUTSIDE ±3 SD across BOTH tails. Only approximately 0.15% lie beyond 3 SD in ONE direction. This simple approach is generally sufficient for Primary FRCA questions.