Social & Preventive Medicine The PEFR of a group of 11 year old girls follow a normal distribution with mean 300 L/min and stardard detion 20 L/min- A About 95 % of the girls have PEFR between 260 and 340 L/min B The girls have healthy lungs C About 5% of girls have PEFR below 260 L/min D All the PEFR must be less than 340 L/min 💡 Explanation The PEFR of a group of 11 year old girls follow a normal distribution with mean 300 L/min and stardard detion 20 L/min- ✓ Correct Answer: A. About 95 % of the girls have PEFR between 260 and 340 L/min