試題詳解

2. Which of the following statements about normal distribution is (are) correct?

 (AB) Bell-shaped distributions are normal distributions. (AC) Approximately 95% of the area of a normal distribution is within three standard deviations of the mean. (AD) The median and mode are not equal for a normal distribution. (AE) Normal distributions can differ in their means and in their standard deviations. (BC) The average of many observations of a random variable with finite mean and variance is itself not a random variable. (BD) Normal distributions are often used in the natural and social sciences to represent real-valued random variables whose distributions are not known.