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': 'The standard normal distribution - \nSelect and explain. \nA. It skewed to the left, B. Has mean =1.0, C. Has standard deviation = 0.0, D. Has variance =1.0', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Standard normal curve\n\nIt is also known as bell curve or Gaussian distribution.\nThe shape of the curve is like a bell → shaped curve.\nThe data is distributed symmetrically on either side of a central value.\nNormal distribution curve looks symmetrical in the dispersion with the largest frequencies in the middle score and tapering down of frequencies towards the highest as well as the lowest score No tail.\nNormal distribution curve is based on mean and standard deviation.\nMean, median and mode all coincide → No skew.\nMean = median = mode = 0\nTotal area of curve is 1.\nIts standard deviation is 1.\nVariance is \xa0\n\nVariance\n\nVariance is squared deviation from mean.\nFor example, if deviation in a curve is 2 standard (2 SD) then variance will be square of this deviation i.e. (2 SD)2.\nSo,\n\nVariance = SD2\nIn normal curve SD is 1.\nSo variance = SD2 =12 =1', 'role': 'assistant'}]