QNT 2020 EXAM 1 QUESTIONS WITH VERIFIED
ANSWERS
A frequency distribution is a tabulation of n data values into classes called bins.
True/False - Answers - True
Explanation: This is the definition of a frequency distribution.
Scatter plots are used to visualize association in samples of paired data (X, Y).
True/False - Answers - True
Explanation: That is exactly what a scatter plot is for.
Outliers are data values that fall beyond ±2 standard deviations from the mean.
True/False - Answers - False
Explanation:
Outliers are 3 standard deviations from the mean
Chebyshev's Theorem says that at most 50 percent of the data lie within 2 standard
deviations of the mean. True/False - Answers - False
Explanation:
At least 75 percent by Chebyshev.
The Empirical Rule assumes that the distribution of data follows a normal curve.
True/False - Answers - True
Explanation:
Unlike Chebyshev, the Empirical Rule assumes a normal population.
If the mean and median of a population are the same, then its distribution is: - Answers -
Symmetric
Explanation:
Any population is symmetric if its mean and median are equal. While the normal and
uniform distributions are symmetric, there are other symmetric populations.
A population consists of the following data: 7, 11, 12, 18, 20, 22, 25. The population
variance is: - Answers - 36.82
Explanation:
Use the population formula or Excel's =VAR.P(Data).
So far this year, stock A has had a mean price of $6.58 per share with a standard
deviation of $1.88, while stock B has had a mean price of $10.57 per share with a
standard deviation of $3.02. Which stock is more volatile? - Answers - They are the
same
Explanation:
They are the same: CVA = 100(1.88/6.58) = 28.57%. CVB = 100(3.02/10.57) = 28.57%.
, Could this function be a PDF? - Answers - No
Explanation:
Area = base × height = 2, which is not 1, so it cannot be a PDF.
The figure shows a standard normal N(0,1) distribution. Find the shaded area.
u=0
o=1
z=+0.44 - Answers - 0.3300
Explanation:
Appendix C.2. gives 1 − P( z < 0.44) = 1 − 0.6700 = 0.3300 = 1 −
NORM.S.DIST(0.44,1).
If the random variable Z has a standard normal distribution, then P(Z ≤ −1.72) is: -
Answers - 0.0427
Explanation:
Use Appendix C or Excel = NORM.S.DIST(−1.72,1).
Which probability model is most appropriate to describe the waiting time (working days)
until an office photocopier breaks down (i.e., requires unscheduled maintenance)? -
Answers - Exponential
Explanation:
Poisson breakdowns suggest exponential waiting time.
The figure shows a standard normal N(0,1) distribution. Find the z value for the shaded
area.
u=0
o=1
z=??
shaded area=0.04 - Answers - -1.75
Explanation:
Appendix C.2 gives P(z < − 1.75) = 0.0401 or use Excel = NORM.S.INV(0.04) = −1.75.
If adult male heights are normally distributed with a mean of 180 cm and a standard
deviation of 7 cm, how high should an aircraft lavatory door be to ensure that 99.9
percent of adult males will not have to stoop as they enter? - Answers - 201.6cm
Explanation: With Excel, we get = NORM.INV(0.999,180,7) = 201.63, or Appendix C
with z = 3.0
A higher confidence level leads to a narrower confidence interval, ceteris paribus.
True/False - Answers - False
Explanation: Higher confidence requires more uncertainty (a wider interval). For
example, z0.025 = 1.960 (for 95 percent confidence) gives a wider interval than z0.05 =
1.645 (for 90 percent confidence). The proffered statement would also hold true for the
Student's t distribution.
ANSWERS
A frequency distribution is a tabulation of n data values into classes called bins.
True/False - Answers - True
Explanation: This is the definition of a frequency distribution.
Scatter plots are used to visualize association in samples of paired data (X, Y).
True/False - Answers - True
Explanation: That is exactly what a scatter plot is for.
Outliers are data values that fall beyond ±2 standard deviations from the mean.
True/False - Answers - False
Explanation:
Outliers are 3 standard deviations from the mean
Chebyshev's Theorem says that at most 50 percent of the data lie within 2 standard
deviations of the mean. True/False - Answers - False
Explanation:
At least 75 percent by Chebyshev.
The Empirical Rule assumes that the distribution of data follows a normal curve.
True/False - Answers - True
Explanation:
Unlike Chebyshev, the Empirical Rule assumes a normal population.
If the mean and median of a population are the same, then its distribution is: - Answers -
Symmetric
Explanation:
Any population is symmetric if its mean and median are equal. While the normal and
uniform distributions are symmetric, there are other symmetric populations.
A population consists of the following data: 7, 11, 12, 18, 20, 22, 25. The population
variance is: - Answers - 36.82
Explanation:
Use the population formula or Excel's =VAR.P(Data).
So far this year, stock A has had a mean price of $6.58 per share with a standard
deviation of $1.88, while stock B has had a mean price of $10.57 per share with a
standard deviation of $3.02. Which stock is more volatile? - Answers - They are the
same
Explanation:
They are the same: CVA = 100(1.88/6.58) = 28.57%. CVB = 100(3.02/10.57) = 28.57%.
, Could this function be a PDF? - Answers - No
Explanation:
Area = base × height = 2, which is not 1, so it cannot be a PDF.
The figure shows a standard normal N(0,1) distribution. Find the shaded area.
u=0
o=1
z=+0.44 - Answers - 0.3300
Explanation:
Appendix C.2. gives 1 − P( z < 0.44) = 1 − 0.6700 = 0.3300 = 1 −
NORM.S.DIST(0.44,1).
If the random variable Z has a standard normal distribution, then P(Z ≤ −1.72) is: -
Answers - 0.0427
Explanation:
Use Appendix C or Excel = NORM.S.DIST(−1.72,1).
Which probability model is most appropriate to describe the waiting time (working days)
until an office photocopier breaks down (i.e., requires unscheduled maintenance)? -
Answers - Exponential
Explanation:
Poisson breakdowns suggest exponential waiting time.
The figure shows a standard normal N(0,1) distribution. Find the z value for the shaded
area.
u=0
o=1
z=??
shaded area=0.04 - Answers - -1.75
Explanation:
Appendix C.2 gives P(z < − 1.75) = 0.0401 or use Excel = NORM.S.INV(0.04) = −1.75.
If adult male heights are normally distributed with a mean of 180 cm and a standard
deviation of 7 cm, how high should an aircraft lavatory door be to ensure that 99.9
percent of adult males will not have to stoop as they enter? - Answers - 201.6cm
Explanation: With Excel, we get = NORM.INV(0.999,180,7) = 201.63, or Appendix C
with z = 3.0
A higher confidence level leads to a narrower confidence interval, ceteris paribus.
True/False - Answers - False
Explanation: Higher confidence requires more uncertainty (a wider interval). For
example, z0.025 = 1.960 (for 95 percent confidence) gives a wider interval than z0.05 =
1.645 (for 90 percent confidence). The proffered statement would also hold true for the
Student's t distribution.
