Question

Chapter 8
1. If the sampled population has a mean 48 and standard deviation 18, then the mean and the standard deviation for the sampling distribution of (X-bar) for n = 9 are:
A. 48 and 18
B. 48 and 9
C. 48 and 6
D. 16 and 3
E. 48 and 3

2. A manufacturing company measures the weight of boxes before shipping them to the customers. If the box weights have a population mean and standard deviation of 90 lbs. and 24 lbs. respectively, then based on a sample size of 36 boxes, the probability that the average weight of the boxes will be more than 94 lbs. is:
A. 34.13%
B. 15.87%
C. 84.13%
D. 56.36%
E. 16.87%

3. Whenever the population has a normal distribution, the sampling distribution of   (X-bar) is normal:
A. For only large sample sizes
B. For only small sample sizes
C. For any sample size
D. Only for samples of size 30 or more

4. If a population distribution is known to be normal, then it follows that:
A. The sample mean must equal the population mean
B. The sample mean must equal the population mean for large samples
C. The sample standard deviation must equal the population standard deviation
D. All of the above
E. None of the above

5. In a manufacturing process a machine produces bolts that have an average length of 3 inches with a variance of .03. If we randomly select three bolts from this process: What is the probability the mean length of the bolt is more than 3.16 inches?
A. 5.48%
B. 97.72%
C. 94.52%
D. 44.52%
E. 2.28%

6. In a manufacturing process a machine produces bolts that have an average length of 3 inches with a variance of .03. If we randomly select three bolts from this process: What is the probability the mean length of the bolt is less than 3.1 inches?
A. 84.13%
B. 100%
C. 71.57%
D. 28.43%
E. 15.87%

Answer 1

1. If the sampled population has a mean 48 and standard deviation 18, then the mean and the standard deviation for the sampling distribution of (X-bar) for n = 9 are:
B. 48 and 9

2. A manufacturing company measures the weight of boxes before shipping them to the customers. If the box weights have a population mean and standard deviation of 90 lbs. and 24 lbs. respectively, then based on a sample size of 36 boxes, the probability that the average weight of the boxes will be more than 94 lbs. is:
B. 15.87%
P(x>94)=?

3. Whenever the population has a normal distribution, the sampling distribution of   (X-bar) is normal:
C. For any sample size
4. If a population distribution is known to be normal, then it follows that:
D. All of the above

5. In a manufacturing process, a machine produces bolts that have an average length of 3 inches with a variance of .03. If we randomly select three bolts from this process: What is the probability the mean length of the bolt is more than 3.16 inches?
A. 5.48%

P(x>3.16)=?

6. In a manufacturing process, a machine produces bolts that have an average length of 3 inches with a variance of .03. If we randomly select three bolts from this process: What is the probability the mean length of the bolt is less than 3.1 inches?
A. 84.13%

P(x<3.1)=?