Practice Quiz III
1. A technician at a plant which produces wire cables selects a simple random sample of 100 cables each
week from among the thousands of cables that are ready for shipping. The cables are subjected to a load
of 1000 pounds. Any cable that breaks under this load is considered to be defective. The quality control
manager has decided that if the proportion of defective cables in the sample exceeds 0.10, then all cables
currently ready for shipping will be tested before they are shipped.
Which of the following is
not
correct?
(a)
The population is all cables produced at the plant that are ready for shipping.
(b)
The sample size is 100 cables (each week).
(c)
The parameter of interest is the proportion in the sample of 1000 that are defective (a strength less
than 1000 pounds).
(d)
If the population proportion is 0.08, it is possible that the sample proportion exceeds 0.10, in
which case all cables ready for shipping will be tested.
2. A Human Resources manager works for a chain of department stores with stores in 30 states. She wants
to take a survey of employees and asks the question: “Is maintaining health care benefits more important
than salary increase?” The proportion of the employees surveyed who say “YES” will be computed.
The manager sends an email to the employees in the state where the company has its headquarters
and asks them to respond to this question. Based on the responses she receives, she computes the
proportion of those responses that are “YES”.
The manager’s assistant proposes an alternative to taking the survey. She suggests selecting a
simple random sample of 8 states that have stores, and then selecting a simple random sample of
employees from the stores in those states.
Which of the following is correct?
(a)
The manager’s sample is a simple random sample
(b)
The assistant’s sample is a simple random sample
(c)
The manager’s sample is more representative
(d)
There is non-response bias in the manager’s sample
3.
The Economic Times
reported a survey that indicated 68% of readers agree with the statement
“Auditors should obtain regulatory clearance before auditing listed companies.”
If the survey result is
based on a random sample of 170 readers of
The Economic Times
, then we should conclude (with high
confidence) that
(a)
68% of all readers agree with the statement.
(b)
Half of all readers agree with the statement.
(c)
Less than half of all readers agree with the statement.
(d)
More than 60% of all readers agree with the statement.

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A confidence interval was used to estimate the proportion of business students that are females. A
random sample of 72 business students generated the following 95% confidence interval: [0.438, 0.642].

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