The probability mass between two standard deviations around the mean for a normal distribution is ________.（ ）
A: 66%
B: 90%
C: 75%
D: 95%
A: 66%
B: 90%
C: 75%
D: 95%
举一反三
- Which of the following about the normal distribution is NOT true? A: Theoretically, the mean, median, and mode are the same B: About 68% of the observations fall within ±1 standard deviation from the mean C: Its parameters are the mean, μ, and standard deviation, σ D: It is a discrete probability distribution.
- 中国大学MOOC: A population distribution is normal with a mean of 18 and standard deviation of 4. A sample of 16 observations is selected and a sample mean computed. What is the probability that the sample mean is more than 18?
- 2.Which of the following about the normal distribution is NOT true A: Theoretically, the mean, median, and mode are the same. B: About 2/3 of the observations fall within ±1 standard deviation from the mean. C: It is a discrete probability distribution. D: Its parameters are the mean, μ, and standard deviation, σ.
- A standard normal distribution is a normal distribution with:
- After preparing the probability distribution of cost outcome for a project, the estimate, with a 15% probability of being exceeded, is approximately one standard deviation （）. A: below the mean B: above the median C: above the mean D: above the median