This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
[{'content': 'In a bell-shaped standard normal curve, mean +-2 standard detions covers: \nSelect and explain. \nA. 60%, B. 65%, C. 95%, D. 99%', 'role': 'user'}, {'content': 'Answer: C \nExplanation: If the distribution of observations is bell-shaped, then even more can be said about the percentage of observations that lay between the mean and +- 2 standard detions. For a bell-shaped distribution, approximately: 67% of the observations lie between the mean +- 1 standard detion 95% of the observations lie between the mean +- 2 standard detions 99.7% of the observations lie between the mean +- 3 standard detions Ref: Dawson B., Trapp R.G. (2004). Chapter 3. Summarizing Data & Presenting Data in Tables & Graphs. In B. Dawson, R.G. Trapp (Eds), Basic & Clinical Biostatistics, 4e.', 'role': 'assistant'}]