商务统计学章节测试课后答案2024春

第六章测试

1.The normal distribution is an example of _______.
A:a bimodal distribution B:an exponential distribution C:a discrete distribution D:a continuous distribution
答案:D
2.The total area underneath any normal curve is _______.
A:equal to the variance B:equal to the mean C:equal to the coefficient of variation D:equal to 1 3.The area to the left of the mean in any normal distribution is _______.
A:equal to 1 B:equal to 0.5 C:equal to the variance D:equal to the mean 4.For any normal distribution, any value less than the mean would have a _______.
A:negative z-score B:negative variance C:positive z-score  D:negative probability of occurring 5.A standardised normal distribution has the following characteristics:
A:the mean is equal to the variance B:the mean is equal to 0 and the variance is equal to 1 C:the mean and variance are both equal to 0 D:he mean and variance are both equal to 1 6.If X is a normal random variable with mean 80 and standard deviation 5, calculate the z-score if X = 88.
A:1.8 B:1.6 C:-1.6 D:-1.8 7.Suppose X is a normal random variable with mean 60 and standard deviation 2. A z-score was calculated for a number, and the z-score is 3.4. What is x?
A:63.4 B:56.6 C:53.2 D:66.8 8.Let X be a normal random variable with mean 20 and standard deviation 4. Find P(16 < X < 22).
A:0.0328 B:0.1498 C:0.4672 D:0.5328 9.Let X be a normal random variable with mean 20 and standard deviation 4. The 90th percentile of X is ____________.
A:20.000 B:26.579 C:22.698 D:25.126 10.A z-score is the number of __________ that a value is from the mean.
A:variances B:miles C:units D:standard deviations