举一反三
- Given an infinite population with a mean of 75 and a standard deviation of 12, the probability that the mean of a sample of 36 observations, taken at random from this population, exceeds 78 is:
- 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?
- A sample of 400 observations will be taken from an infinite population. The population proportion equals 0.8. The probability that the sample proportion will be greater than 0.83 is
- A researcher is interested in testing to determine if the mean of population one is greater than the mean of population two. The null hypothesis is that there is no difference in the population means (i.e. the difference is zero). The alternative hypothesis is that there is a difference (i.e. the difference is not equal to zero). He randomly selects a sample of 9 items from population one resulting in a mean of 14.3 and a standard deviation of 3.4. He randomly selects a sample of 14 items from population two resulting in a mean of 11.8 and a standard deviation 2.9. He is using an alpha value of .10 to conduct this test. Assuming that the populations are normally distributed, the critical t-value from the table is _______.
- When measuring the dispersion of the sample mean, the statistics to be used are ( ) . A: Coefficient of variation B: The standard deviation C: Standard deviation of the mean D: Range value
内容
- 0
The standard error of the mean is never larger than the standard deviation of the population.
- 1
From a population of 500 elements, a sample of 225 elements is selected. It is known that the variance of the population is 900. The standard error of the mean is approximately
- 2
The difference between the sample mean and the population mean is called the: A: population deviation. B: population standard deviation. C: standard error of the mean. D: sampling error.
- 3
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.
- 4
The difference between the sample mean and the population mean is called the sampling error.