Download MULTIPLE CHOICE. Choose the one alternative that best completes

M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
1) If the expectation of a sampling distribution is located at the parameter it is estimating, then
we call that sampling distribution
A) unb iased . B) a m inim um variance. C) biased . D) random .
2) For air travelers, one of the biggest complaints is of the waiting time between when the
airplane tax is away from the term inal until the flight take s off. This w aiting time is know n to
have a skew ed-right distribution with a m ean of 10 minu tes and a standard d eviation of 8
minutes. Suppose 100 flights have been randomly sampled. Describe the sampling distribution of
the mean waiting time between when the airplane taxis away from the terminal and when the
flight takes o ff for th ese 100 fligh ts.
A) Distributio n is ske we d-right with me an = 10 m inutes and stand ard error = 0.8 m inute s.
B) D istribu tion is sk ew ed-right w ith m ean = 10 m inutes and stand ard error = 8 m inute s.
C) D istribu tion is ap proxim ately n orm al with m ean = 10 m inute s and stand ard error = 0.8
minute s.
D) D istribu tion is ap proxim ately n orm al with m ean = 10 m inute s and stand ard error = 8 m inute s.
3) Why is the Central Limit Theorem so important to the study of sampling distributions?
A) It allow s us to disre gard the size of the sam ple se lected wh en the po pulation is n ot norm al.
B) It allows us to disregard the shape of the sampling distribution when the size of the population
is large.
C) It allows us to disre gard the size of the pop ulation w e are sam pling from .
D) It allows us to disre gard the sh ape of the pop ulation w hen n is large.
4) Suppo se a sample of n = 50 items is drawn from a population of manufactured products and
the w eight, X, of each item is recorded. Prior exp erience has show n that the weight has a
probability distribution with
= 6 ounces and
= 2.5 ounces. Which of the following is true
about the sampling distribution of the sample mean if a sample of size 15 is selected?
A) The me an of the sampling distrib ution is 6 oun ces.
B) T he standard dev iation of the sampling distrib ution is 2.5 ounces.
C) T he sh ape of the sam ple d istribu tion is ap proxim ately n orm al.
D) A ll of the abov e are corre ct.
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
5) The average score of all pro golfers for a particular course has a m ean of 70 and a standard
deviation of 3.0. Suppose 36 golfers played the course today. Find the probability that the average
score of the 36 golfers exceed ed 71.
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
6) Sales prices of baseball cards from the 1960s are known to possess a skewed-right distribution
with a mean sale price of $5.25 and a standard deviation of $2.80. Suppose a random sample of
100 cards from the 1960s is selected . Describe the sam pling distrib ution for the sam ple m ean sale
price of the selected card s.
A) Sk ewed -right with a me an of $5.25 and a standard error of $2.80
B) No rmal w ith a mean of $5.25 and a standard error of $0.28
C) Skew ed-right w ith a mean of $5.25 and a standard error of $0.28
D) N ormal w ith a mean of $5.25 and a standard error of $2.80
7) Major league baseball salaries averaged $1.5 million with a standard deviation of $0.8 million
in 1994. Suppo se a sam ple of 100 m ajor league players w as taken. Find the approxim ate
probab ility that the averag e salary of the 100 players exceeded $1 m illion.
A) A pproxim ately 0 B) 0.2357
C) 0.7357 D) Ap proxim ately 1
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
8) At a com puter m anu factu ring com pan y, the actua l size of com puter ch ips is norm ally
distributed with a mean of 1 centimeter and a standard deviation of 0.1 centimeter. A random
sample of 12 computer chips is taken. Above w hat value do 2.5% of the sample means fall?
TRU E/FA LSE . Write 'T' if the statement is true and 'F' if the statemen t is false.
9) Tru e or F alseA s the sa mple size increases, the standard error of the me an inc rease s.
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
10) The am oun t of tim e req uired for an oil and filter change on an au tom obile is norm ally
distrib uted with a mean of 45 m inute s and a stand ard dev iation of 10 m inute s. A rand om sam ple
of 16 cars is selected. So, 90% of the sample means will be greater than what value?
SH OR T A NS W ER . Write th e wo rd or p hrase th at best co mpletes ea ch statement or an swers
the question.
11) A manufacturer of pow er too ls claim s that the averag e am oun t of tim e req uired to assem ble
their top-of-the-line table saw is 80 minutes with a standard deviation of 40 minutes. Suppose a
random sample of 64 purchasers of this table saw is taken. The standard deviation of the
sam pling distrib ution of the sam ple m ean is __________ min utes.
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
TABLE 6-3
lifetimes of a certain brand of light bulbs are known to be normally distributed with a mean of
1,600 h ours and a stand ard dev iation of 400 hours. A rand om sam ple of 64 of th ese light bu lbs is
taken.
12) Referring to Table 6-3, the probability is 0.15 that the sample mean lifetime is more than how
many hours?
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
13) If yo u w ere constr uctin g a 99% confidence interv al of the pop ulation m ean based on a sam ple
of n=25 where the standard deviation of the sample s = 0.05, the critical value of t will be
A) 2.7969. B) 2.7874. C) 2.4922. D) 2.4851.
14) Suppo se a 95% con fidence interval for
turns out to be (1,000, 2,100). Give a definition of
wh at it means to be "95% confident" in an infe rence.
A) In repeated sampling, the population parameter would fall in the given interval 95% of the
time .
B) In repeated sam pling , 95% of the interv als con struc ted wo uld contain the pop ulation m ean.
C) 95% of the observatio ns in th e entire popu lation fall in the given interv al.
D) 95% of the obse rvatio ns in th e sam ple fall in the given interv al.
15) In the construction of confidence intervals, if all other quantities are unchanged, an increase
in the sam ple size w ill lead to a __________ interval.
A) narrower B) wider C) less significant D) biased
16) A m ajor departme nt store chain is interested in estimating the average am ount its credit card
custome rs spent on their first visit to the chain's new store in the mall. Fifteen credit card
accounts w ere random ly sampled and analyzed with the following results XBA R = $ 50.50 and
the sample v ariance = 400. C onstr uct a 95% confidence interv al for the averag e am oun t its cred it
card custo mers sp ent on their first visit to the ch ain's ne w store in the m all.
A) $50.50 \'B1 $9.09 B) $50.50 \'B1 $10.12
C) $50.50 \'B1 $11.00 D) $50.50 \'B1 $11.08
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
17) A univ ersity system enro lling hu ndred s of tho usan ds of stud ents is considering a change in
the way students pay for their education. Presently the students pay $55 per credit hour. The
university system administrators are contemplating charging each student a set fee of $750 per
quarter, regardless of how many credit hours each takes. To see if this proposal would be
economically feasible, the administrators would like to know how many credit hours, on the
average , each stud ent tak es per qu arter. A random sam ple of 250 stu dents yie lds a m ean of 14.1
credit hours per quarter and a standard deviation of 2.3 credit hours per quarter. Suppose the
administration wanted to estimate the mean to within 0.1 hours at 95% reliability and assumed
that the sample standard deviation provide d a good estimate for the popu lation standard
deviation. How large a sample would they need to take?
18) As an aid to the establishm ent of personn el require me nts, the director of a hospital wishes to
estimate the mean number of people who are admitted to the emergency room during a 24-hour
period. The director randomly selects 64 different 24-hour periods and determines the number of
adm issions for each. For this sam ple,
= 19.8 and
= 25. Estimate the mean number of
adm issions per 24-h our period w ith a 95% confidence interv al.
19) A university dean is interested in determining the proportion of students who receive some
sort of financ ial aid. Rather than examine the records for all studen ts, the dean rando mly selects
200 students and finds that 118 of them are receiving financial aid. Use a 90% confiden ce interval
to estim ate the true proportion of stud ents wh o receive financial aid.
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
20) An economist is interested in studying the incomes of consumers in a particular region. The
population standard deviation is known to be $1,000. A random sample of 50 individuals resulted
in an average income of $15,000. What is the upper end point in a 99% confidence interval for the
average income?
A) $15,052 B) $15,141 C) $15,330 D) $15,364
21) The head librarian at the L ibrary of C ongre ss has aske d her assistant for an interval estim ate
of the mean num ber of books che cked ou t each day. The assistant provides the following interval
estimate from 740 to 920 book s per day. If the head librarian know s that the population standard
deviation is 150 books checked out per day, and she asked her assistant for a 95% confidence
interval, approximately how large a sample did h er assistant use to determine the interval
estimate?
A) 125 B) 13 C ) 11 D) 4
SH OR T A NS W ER . Write th e wo rd or p hrase th at best co mpletes ea ch statement or an swers
the question.
22) A quality control engineer is interested in estimating the proportion of defective items
coming off a production line. In a sample of 300 items, 27 are defective. A 90% confidence interval
for the p roportion of de fective item s from this prod uction line w ould go from __________ to
_____ _____.
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
23) The head of a computer science department is interested in estimating the proportion of
students entering the department who will choose the new computer engineering option.
Suppose there is no information about the proportion of students who might choose the option.
What size sample should the department head take if she wants to be 95% confident that the
estimate is within 0.10 of the true proportion?
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
1) A
2) C
3) D
4) A
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
5) 0.0228
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
6) B
7) D
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
8) 1.057
TRU E/FA LSE . Write 'T' if the statement is true and 'F' if the statemen t is false.
9) FALSE
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
10) 41.8 minutes
SH OR T A NS W ER . Write th e wo rd or p hrase th at best co mpletes ea ch statement or an swers
the question.
11) 5
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
12) 1,651.82 hours
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
13) A
14) B
15) A
16) D
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
17) n = 2033
18) 19.8 \'B1 1.249
19) 0.59 \'B10.057
M UL TIPL E C HO ICE . Cho ose the one alternative that b est com pletes th e statem ent or an swers
the question.
20) D
21) C
SH OR T A NS W ER . Write th e wo rd or p hrase th at best co mpletes ea ch statement or an swers
the question.
22) 0.063 to 0.117
ESSA Y. W rite you r answ er in the space provided or on a separate sheet of p aper.
23) 97