Bus 3265 COBA sp2020
For which of the following would a control chart for attributes not be appropriate?
Length of metal rods
What measures the central tendency of a set of data?
Mean
Which measure of central tendency can be used for both numerical and categorical variables?
Mode
For a p-chart or c-chart, what is the implication of a negative value for the LCL?
The LCL can effectively be rounded up to 0.
Which of the following is a continuous quantitative (numerical) variable?
The amount of milk in a 2-liter carton
Which of the following is sensitive to extreme values?
The arithmetic mean
The power of a statistical test is
the probability of rejecting H0 when it is false
The test for the equality of two population variances is based on
the ratio of the 2 sample variances
A Type I error is committed when
you reject a null hypothesis that is true
Which of the following is most likely a population as opposed to a sample?
registered voters in a county
The standard deviation is an example of what?
Fishbone diagramming
How many tissues should the Kimberly Clark Corporation package of Kleenex contain? Researchers determined that 60 tissues is the mean number of tissues used during a cold. Suppose a random sample of 100 Kleenex users yielded the following data on the number of tissues used during a cold: X = 52, S = 22. Give the null and alternative hypotheses to determine if the number of tissues used during a cold is less than 60.
H0 : m ³ 60 and H1 : m < 60.
If the outcome of event A is not affected by event B, then events A and B are said to be
independent
If event A and event B cannot occur at the same time, then events A and B are said to be
mutually exclusive
In testing a hypothesis using the c 2 test, the theoretical frequencies are based on the
null hypothesis
What is a control chart that monitors the proportion of defects in a sample?
p-chart
Which of the following is not associated with descriptive statistics?
proportion
P-charts are used to measure
proportion of items in a sample that is defective
Which of the following would imply that data observations are closely clustered around the mean?
Small range and small standard deviation
The A2 factor includes how many standard deviations of ranges?
3
The center line of a control chart represents what?
Mean
. In a perfectly symmetrical distribution
the median equals the arithmetic mean
. Major league baseball salaries averaged $3.26 million with a standard deviation of $1.2 million in a certain year in the past. Suppose a sample of 100 major league players was taken. What was the standard error for the sample mean salary?
$0.12 million
The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. If a sample of 64 fish yields a mean of 3.4 pounds, what is probability of obtaining a sample mean this large or larger?
0.0228
According to a survey of American households, the probability that the residents own 2 cars if annual household income is over $50,000 is 80%. Of the households surveyed, 60% had incomes over $50,000 and 70% had 2 cars. The probability that the residents of a household do not own 2 cars and have an income over $50,000 a year is:
0.12
What is the probability of a Type I error for a control chart with limits set at ± 3 standard deviations from the mean?
0.26%
If we know that the length of time it takes a college student to find a parking spot in the library parking lot follows a normal distribution with a mean of 3.5 minutes and a standard deviation of 1 minute, find the probability that a randomly selected college student will find a parking spot in the library parking lot in less than 3 minutes
0.3085
The employees of a company were surveyed on questions regarding their educational background (college degree or no college degree) and marital status (single or married). Of the 600 employees, 400 had college degrees, 100 were single, and 60 were single college graduates. The probability that an employee of the company is married and has a college degree is:
0.567
The employees of a company were surveyed on questions regarding their educational background (college degree or no college degree) and marital status (single or married). Of the 600 employees, 400 had college degrees, 100 were single, and 60 were single college graduates. The probability that an employee of the company is single or has a college degree is
0.733
If we know that the length of time it takes a college student to find a parking spot in the library parking lot follows a normal distribution with a mean of 3.5 minutes and a standard deviation of 1 minute, find the probability that a randomly selected college student will take between 2 and 4.5 minutes to find a parking spot in the library parking lot.
0.7745
Referring to Scenario 2-5, if 100 calls were randomly sampled, how many calls lasted 15 minutes or longer?
26
Upper and lower control limits are usually set at ± how many standard deviations from the mean?
3.0
Six-sigma quality implies how many average defects per million?
3.4
If we are testing for the difference between the means of 2 independent populations presuming equal variances with samples of n1 = 20 and n2 = 20, the number of degrees of freedom is equal to
38
Causes of variation that can be identified and eliminated are called what?
Assignable
The owner of a fish market determined that the mean weight for a catfish is 3.2 pounds with a standard deviation of 0.8 pound. A citation catfish should be one of the top 2% in weight. Assuming the weights of catfish are normally distributed, at what weight (in pounds) should the citation designation be established?
4.84 pounds
The following are the duration in minutes of a sample of long-distance phone calls made within the continental United States reported by one long-distance carrier. Relative Time (in Minutes) Frequency 0 but less than 5 0.37 5 but less than 10 0.22 10 but less than 15 0.15 15 but less than 20 0.10 20 but less than 25 0.07 25 but less than 30 0.07 30 or more 0.02 What is the width of each class?
5 minutes
Referring to Scenario 2-5, if 1,000 calls were randomly sampled, how many calls lasted under 10 minutes?
590
When testing for independence in a contingency table with 3 rows and 4 columns, there are degrees offreedom
6
What process width is typically used when computing the process capability index Cp?
6s
Thirty-six of the staff of 80 teachers at a local intermediate school are certified in Cardio- Pulmonary Resuscitation (CPR). In 180 days of school, about how many days can we expect that the teacher on bus duty will likely be certified in CPR?
81 days
For the standard normal distribution, how much confidence is provided within 2 standard deviations above and below the mean?
95.44%
Assuming that data exhibit a normal distribution, control limits set at ± 3 standard deviations from the mean capture how much common variation?
99.74%
You have collected data on the monthly seasonally adjusted civilian unemployment rate for the United States over a 10-year period. Which of the following is the best for presenting the data?
A time-series plot
An OC curve is an example of what?
Acceptance sampling
Researchers suspect that the average number of units earned per semester by college students is rising. A researcher at Calendula College wishes to estimate the number of units earned by students during the spring semester at Calendula. To do so, he randomly selects 100 student transcripts and records the number of units each student earned in the spring term. He found that the average number of semester units completed was 12.96 units per student. Identify the population of interest to the researcher
All Calendula College students enrolled in the spring
Most analysts focus on the cost of tuition as the way to measure the cost of a college education. But incidentals, such as textbook costs, are rarely considered. A researcher at Drummand University wishes to estimate the textbook costs of first-year students at Drummand. To do so, she monitored the textbook cost of 250 first-year students and found that their average textbook cost was $600 per semester. Identify the population of interest to the researcher.
All first-year Drummand University students
The probability that house sales will increase in the next 6 months is estimated to be 0.25. The probability that the interest rates on housing loans will go up in the same period is estimated to be The probability that house sales or interest rates will go up during the next 6 months is estimated to be 0.89. The events increase in house sales and no increase in house sales in the next 6 months are
B) mutually exclusive C) collectively exhaustive. *D) Both (b) and (c)
On a control chart, what separates common from assignable causes of variation?
Control limits
The Wall Street Journal recently published an article indicating differences in perception of sexual harassment on the job between men and women. The article claimed that women perceived the problem to be much more prevalent than did men. One question asked of both men and women was: "Do you think sexual harassment is a major problem in the American workplace?" 24% of the men compared to 62% of the women responded "Yes." Assuming W designates women's responses and M designates men's, what hypothesis should The Wall Street Journal test in order to show that its claim is true?
H0: pW - p M £ 0 versus H1: pW - p M > 0
Which of the following statements about the median is not true?
It is equal to Q2
Which of the following statistics is not a measure of central tendency?
Q3
What is a control chart that monitors changes in the dispersion or variability of a process?
R-chart
All processes will have what type of variation?
Random
What measures the difference between the largest and smallest observations in a set of data?
Range
What is the first step that should be taken if an observation falls below the lower control limit on a control chart?
Search for assignable causes
What measures symmetry of a distribution?
Skewness
A c-chart is an example of what?
Statistical process control
A p-chart is an example of what?
Statistical process control
An x-bar chart is an example of what?
Statistical process control
What technique answers the question of whether the process is functioning properly or not?
Statistical process control
What is a distribution called when the same numbers of observations are below the mean as are above the mean?
Symmetric
A study is under way in Yosemite National Forest to determine the adult height of American pine trees. Specifically, the study is attempting to determine what factors aid a tree in reaching heights greater than 60 feet tall. It is estimated that the forest contains 25,000 adult American pines. The study involves collecting heights from 250 randomly selected adult American pine trees and analyzing the results. Identify the population from which the study was sampled.
The 25,000 adult American pine trees in the forest
A study is under way in Yosemite National Forest to determine the adult height of American pine trees. Specifically, the study is attempting to determine what factors aid a tree in reaching heights greater than 60 feet tall. It is estimated that the forest contains 25,000 adult American pines. The study involves collecting heights from 250 randomly selected adult American pine trees and analyzing the results. Identify the sample in the study
The 250 randomly selected adult American pine trees
Most analysts focus on the cost of tuition as the way to measure the cost of a college education. But incidentals, such as textbook costs, are rarely considered. A researcher at Drummand University wishes to estimate the textbook costs of first-year students at Drummand. To do so, she monitored the textbook cost of 250 first-year students and found that their average textbook cost was $600 per semester. Identify the sample in the study.
The 250 students that were monitored
Which of the following would be an appropriate alternative hypothesis?
The mean of a population is greater than 55
Which of the arithmetic mean, median, mode, and geometric mean are resistant measures of central tendency?
The median and mode only
Which of the following is a discrete quantitative (numerical) variable?
The number of employees of an insurance company
Which of the following would be an appropriate alternative hypothesis?
The population proportion is less than 0.65
Which of the following would be an appropriate null hypothesis?
The population proportion is not less than 0.65
Consider a p-chart measuring the percentage of defective light bulbs. If the LCL is .04 and a sample has 1% defects, what is the implication?
The process is out of control even though the variation is "good."
Which of the following is most likely a parameter as opposed to a statistic?
The proportion of females registered to vote in a county
Which of the following statements is not true about the level of significance in a hypothesis test?
The significance level is another name for Type II error
A survey claims that 9 out of 10 doctors recommend aspirin for their patients with headaches. To test this claim against the alternative that the actual proportion of doctors who recommend aspirin is less than 0.90, a random sample of 100 doctors was selected. Suppose you reject the null hypothesis. What conclusion can you reach?
There is sufficient evidence that the proportion of doctors who recommend aspirin is less than 0.90.
What is the term for the probability that a value falling outside the control limits is still due to normal variation?
Type I error
The different characteristics that can be measured by control charts can be divided into what two groups?
Variables and attributes
An entrepreneur is considering the purchase of a coin-operated laundry. The current owner claims that over the past 5 years, the mean daily revenue was $675 with a population standard deviation of $75. A sample of 30 days reveals a daily mean revenue of $625. If you were to test the null hypothesis that the daily mean revenue was $675, which test would you use?
Z-test of a population mean
The chancellor of a major university was concerned about alcohol abuse on her campus and wanted to find out the proportion of students at her university who visited campus bars on the weekend before the final exam week. Her assistant took a random sample of 250 students. The answer on "whether you visited campus bars on the weekend before the final exam week" from students in the sample is an example of
a categorical variable
Researchers are concerned that the weight of the average American school child is increasing implying, among other things, that children's clothing should be manufactured and marketed in larger sizes. If X is the weight of school children sampled in a nationwide study, then X is an example of
a continuous variable
To monitor campus security, the campus police office is taking a survey of the number of students in a parking lot each 30 minutes of a 24-hour period with the goal of determining when patrols of the lot would serve the most students. If X is the number of students in the lot each period of time, then X is an example of
a discrete variable
The portion of the universe that has been selected for analysis is called
a sample
The standard error of the mean for a sample of 100 is 30. In order to cut the standard error of the mean to 15, we would
increase the sample size to 400.
The standard error of the mean
a) is never larger than the standard deviation of the population. b) decreases as the sample size increases. c) measures the variability of the mean from sample to sample. *d) All of the above.
If we wish to determine whether there is evidence that the proportion of items of interest is the same in group 1 as in group 2, the appropriate test to use is
a) the Z test. b) the c 2 test. *c) Both a) and b).
In a perfectly symmetrical bell-shaped "normal" distribution
a) the arithmetic mean equals the median. b) the median equals the mode. c) the arithmetic mean equals the mode. *d) All the above
The manager of the customer service division of a major consumer electronics company is interested in determining whether the customers who have purchased a Blu-ray player made by the company over the past 12 months are satisfied with their products. The population of interest is
all the customers who have bought a Blu-ray player made by the company over the past 12 months.
The standard error of the population proportion will become larger
as population proportion approaches 0.50.
What type of probability distribution will most likely be used to analyze warranty repair needs on new cars in the following problem? The service manager for a new automobile dealership reviewed dealership records of the past 20 sales of new cars to determine the number of warranty repairs he will be called on to perform in the next 90 days. Corporate reports indicate that the probability any one of their new cars needs a warranty repair in the first 90 days is 0.05. The manager assumes that calls for warranty repair are independent of one another and is interested in predicting the number of warranty repairs he will be called on to perform in the next 90 days for this batch of 20 new cars sold.
binomial distribution
If either event A or event B must occur, then events A and B are said to be
collectively exhaustive
The Six Sigma approach is organized around a _______ plan known as ________.
five step DMAIC
The Central Limit Theorem is important in statistics because
for a large n, it says the sampling distribution of the sample mean is approximately normal, regardless of the shape of the population.
A process chart is a
graph that show whether a sample falls within the common or normal range
A completely randomized design
has only one factor with several treatment groups
A selection of raffle tickets from a large bowl is an example of
sampling without replacement
Sampling distributions describe the distribution of
statistics.
What are the two aspects to implementing the six-sigma concept?
technical tools and people involvement
A is a numerical quantity computed from the data of a sample and is used in reaching a decision on whether or not to reject the null hypothesis
test statistic
In a right-skewed distribution
the median is less than the arithmetic mean.
Statistical process control tools are used most frequently because
they are helpful in measuring and evaluating the quality of products
If the expected value of a sample statistic is equal to the parameter it is estimating, then we call that sample statistic
unbiased
What is a control chart that monitors changes in the mean value of a process?
x-bar chart
What are the four most common control charts?
x-bar, R, p, c
