The demand for a product for the last six years has been 15, 15, 17, 18, 20, and 19. The
manager wants to predict the demand for this time series using the following simple
linear trend equation: trt = 12 + 2t. Use this equation to forecast the demand for this
product, and then calculate the MSD.
A. MSD = 6
B. MSD = 3.3333
C. MSD = 7.0
D. MSD = 2
E. MSD = 2.4
If the sampled population is finite and at least _____ times larger than the sample size,
we treat the population as infinite.
A. 5
B. 20
C. 30
D. 10
If the random variable x is normally distributed, ______ percent of all possible
observed values of x will be within three standard deviations of the mean.
A. 68.26
B. 95.44
C. 99.73
D. 100
E. None of the other choices is correct.
If events A and B are mutually exclusive, calculate P(A|B).
A. Cannot be determined.
B. 0
C. 1
D. 0.50
In the context of the hypergeometric distribution, r is
A. sample size.
B. the number of items in the population that are successes.
C. the number of items that are sampled without replacement.
D. the number of items in the sample that are successes.
Find z when the area between z and −z is .9030.
A. 1.50
B. 1.30
C. 0.12
D. 1.66
Which of the following is the best analytic dashboard graphical method for visualizing
hierarchical information?
A. bullet graph
B. sparkline
C. treemap
D. gauge
A pharmaceutical company manufacturing flu test kits wants to determine the
probability of a teenager not having the flu when the test results indicate that they do. It
is estimated that the probability of a positive test for flu among potential users of the kit
is 10 percent. According to the company laboratory test results, 1 out of 100
noninfected teenagers tested as having the flu (false positive). On the other hand, 1 out
of 200 teenagers with the flu tested as not having the active virus (false negative). A
teenager has just used the flu test kit manufactured by the company, and the results
showed she has the flu. What is the probability that she does not have the flu?
A. 90%
B. 0.9%
C. 8.3%
D. 91.7%
E. 10.85%
When the moving average method is used to estimate the seasonal factors with
quarterly sales data, a ______ period moving average is used.
A. 2
B. 3
C. 4
D. 5
E. 8
A motorcycle manufacturer produces the parts for its vehicles in different locations and
transports them to its plant for assembly. In order to keep the assembly operations
running efficiently, it is vital that all parts be within specification limits. One important
part used in the assembly is the engine camshaft, and one important quality
characteristic is the case hardness depth. Specifications state that the hardness depth
must be between 3.0 mm and 6.0 mm. To investigate the process, the quality control
engineer selected 25 daily subgroups of n = 5 and measured the hardness depth. The
process yielded a mean of the means = 4.50 and an average range = 1.01. Assuming
that the process is in statistical control, calculate the natural tolerance limits for the
process.
A. [1.47, 7.53]
B. [3.197, 5.803]
C. [3.729, 5.271]
D. [4.066, 4.934]
When constructing a confidence interval for a population mean, if a population is
normally distributed and a small sample is taken, then the distribution of is based on
the ____________ distribution.
A. z
B. t
C. neither the z nor the t distribution
D. both the z and the t distribution
An observation separated from the rest of the data is a(n) ___________.
A. absolute extreme
B. outlier
C. mode
D. quartile
In 20 samples, there are 80 units defective. If each sample consists of 100 units, find the
appropriate UCL and the LCL for the p chart.
A. [.0269, .0531]
B. [.0204, .0596]
C. [.0380, .0420]
D. [0, .0988]
The lifetime of a stereo component is exponentially distributed with mean 1,000 days.
What is the probability that the lifetime is greater than or equal to 700 days?
A. .7603
B. .5034
C. .2397
D. .4966
Which of the following is an advantage of a confidence interval estimate over a point
estimate for a population parameter?
A. Interval estimates are more precise than point estimates.
B. Interval estimates are less accurate than point estimates.
C. Interval estimates are both more accurate and more precise than point estimates.
D. Interval estimates take into account the fact that the statistic being used to estimate
the population parameter is a random variable.
As the stated confidence level decreases, the width of the confidence interval
_______________.
A. stays the same
B. decreases
C. increases
Suppose that and R charts based on subgroups of size 4 are being used to monitor the
tire diameter of a new radial tire. The and R charts are found to be in statistical control,
with = 50.5, = 1.25 inches. A histogram of the tire diameter measurements indicates
that these measurements are approximately normally distributed. Compute the natural
tolerance limits for this process.
A. [48.68, 52.32]
B. [49.89, 51.11]
C. [48.86, 52.14]
D. [46.75, 54.25]
Find the z-score for an IQ test score of 92 when the mean is 100 and the standard
deviation is 15.
A. 0.53
B. 0.77
C. −0.77
D. −0.53
E. −8.00
A fastener company produces a certain type of bolt for the automobile industry with a
nominal (target) length of 2.00 inches. The specifications for the length of the bolt are
2.00 .006 inches. An automobile manufacturer will only purchase from this company if
the sigma level of capability of the process is at least 4. If the process mean is equal to
2.001, determine the maximum process standard deviation necessary for the fastener
manufacturing company in order to qualify as a supplier for the automobile
manufacturing company.
A. .0125
B. .005
C. .00125
D. .00025
The weight of a product is normally distributed with a mean of four ounces and a
variance of .25 squared ounces. What is the probability that a randomly selected unit
from a recently manufactured batch weighs more than 5 ounces?
A. .0228
B. .9772
C. 0.000
D. 1.00
In testing the difference between the means of two independent populations, the
variances of the two samples can be pooled if the population variances are assumed to
____________.
A. be unequal
B. be greater than the mean
C. sum to 1
D. be equal
A random sample of size 36 is taken from a population with mean 50 and standard
deviation 5. Find P( < 48).
A. .0082
B. .8330
C. .0999
D. .1389
Find z when the area to the left of z is .6700.
A. 0.75
B. 0.44
C. −0.44
D. −0.75
An important part of the customer service responsibilities of a cable company is the
speed with which trouble in service can be repaired. Historically, the data show that the
likelihood is 0.75 that troubles in a residential service can be repaired on the same day.
For the first five troubles reported on a given day, what is the probability that all five
will be repaired on the same day?
A. .0010
B. .6328
C. .9990
D. .2373
In order to approximate the binomial distribution using the normal distribution, the
following condition(s) must be met if p is near 1.
A. np > 5 only
B. n must be larger than just meeting the condition of np > 5.
C. n can be as small as np > 5.
D. n > 5
While conducting experiments, a marine biologist selects water depths from a
uniformly distributed collection that vary between 2.00 m and 7.00 m. What is the
standard deviation of the water depth?
A. 1.4
B. 2.6
C. 2.5
D. 4.5
Recently, a case of food poisoning was traced to a particular restaurant chain. The
source was identified and corrective actions were taken to make sure that the food
poisoning would not reoccur. Despite the response from the restaurant chain, many
consumers refused to visit the restaurant for some time after the event. A survey was
conducted three months after the food poisoning occurred, with a sample of 319 former
customers contacted. Of the 319 contacted, 29 indicated that they would not go back to
the restaurant because of the potential for food poisoning. Construct a 95 percent
confidence interval for the true proportion of the market who still refuse to visit any of
the restaurants in the chain three months after the event.
A. [.059, .122]
B. [.090, .091]
C. [.000, .196]
D. [.240, .339]
E. [.118, .244]
If the sampled population has a mean of 48 and standard deviation of 16, then the mean
and the standard deviation for the sampling distribution of for n = 16 are
A. 4 and 1.
B. 12 and 4.
C. 48 and 4.
D. 48 and 1.
E. 48 and 16.
In order to test the effectiveness of a drug called XZR designed to reduce cholesterol
levels, the cholesterol levels of 9 heart patients are measured before they are given the
drug. The same 9 patients use XZR for two continuous months. After two months of
continuous use, the cholesterol levels are measured again. The comparison of
cholesterol levels before versus after the administration of the drug is an example of
testing the difference between two ____________.
A. samples of equal variances
B. independent samples
C. paired samples
D. samples of unequal variances
A survey of the wine market has shown that the preferred wine for 17 percent of
Americans is merlot. A wine producer in California, where merlot is produced, believes
the figure is higher in California. She contacts a random sample of 550 California
residents and asks which wine they purchase most often. Suppose 115 reply that merlot
is the primary wine. Calculate the appropriate test statistic to test the hypotheses.