The weekly salaries of teachers in one state are normally distributed with a mean of ￥490 and a standard deviation of ￥45. What is the probability that a randomly selected teacher earns more than ￥525 a week?( )
A: 0.2823
B: 0.1003
C: 0.7823
D: 0.2177
A: 0.2823
B: 0.1003
C: 0.7823
D: 0.2177
举一反三
- 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 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 _______.
- 大写“人民币叁拾柒元玖角整”写成小写应是（）。 A: ￥37.9 B: ￥37.9- C: ￥37.90 D: ￥37.90
- Indicolite的市场价格大约是（ ） A: ￥500/ct B: ￥3800/ct C: ￥6000/ct D: ￥1万/ct
- A sample of size 40 is to be taken from an infinite population whose mean and standard deviation are 68 and 12, respectively. The probability that the sample mean will be larger than 70 is: