# CUNY Bronx Community College Standard Deviation Mathematics Questions

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i don’t need the process. i just need the answers.I questionary is in a weBWork system.if there is any wrong answer it wont accept it and the system would let me know which one is wrong, then i will let you know which one isnt correct.

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1)
A random sample of 20 U.S. weddings yielded the following data on wedding costs in dollars:
8944, 23989, 18464, 28681, 30364, 18838, 10644, 32438, 32115, 5510,
15200, 11732, 31979, 29310, 11035, 12701, 27406, 20589, 19212, 5442
a) Use the data to obtain a point estimate for the population mean wedding cost,
weddings. Note: The sum of the data is 394593.
b) Is your point estimate in part (a) likely equal to
4) A random sample of
, of all recent U.S.
exactly (yes or no)?
measurements was selected from a population with standard
deviation
and unknown mean
of the following situations:
. Calculate a
% confidence interval for
for each
(a)
(b)
(c)
(d) In general, we can say that for the same confidence level, increasing the sample size the margin of
error (width) of the confidence interval. (Enter: ”DECREASES”, ”DOES NOT CHANGE” or
”INCREASES”, without the quotes.)
6) For 30 randomly selected Rolling Stones concerts, the mean gross earnings is 2.45 million dollars.
Assuming a population standard deviation gross earnings of 0.46 million dollars, obtain a 99% confidence
interval for the mean gross earnings of all Rolling Stones concerts (in millions).
Confidence interval: ( , ).
b) Which of the following is the correct interpretation for your answer in part (a)?
A. We can be 99% confident that the mean gross earnings for this sample of 30 Rolling Stones concerts lies
in the interval
B. There is a 99% chance that the mean gross earnings of all Rolling Stones concerts lies in the interval
C. We can be 99% confident that the mean gross earnings of all Rolling Stones concerts lies in the interval
D. None of the above
7) A random sample of
observations produced a mean of
normal distribution and a standard deviation
(a) Find a
% confidence interval for
(b) Find a
% confidence interval for
from a population with a
.
8) A study of the career paths of hotel general managers sent questionnaires to an simple random sample
of 200 hotels belonging to major U.S. hotel chains. There were 92 responses. The average time these 92
general managers had spent with their current company was 10.82 years. (Take it as known that the
standard deviation of time with the company for all general managers is 3 years.)
Find the margin of error for an 85% confidence interval to estimate the mean time a general manager had
spent with their current company. Round your answer to 2 decimal places.
9) Starting salaries of 110 college graduates who have taken a statistics course have a mean of \$44,260.
Suppose the distribution of this population is approximately normal and has a standard deviation of
\$8,825.
Using an 95% confidence level, find both of the following:
(a) The margin of error E:
(b) The confidence interval for the mean
:
10) Suppose you have selected a random sample of
distribution. Compare the standard normal
the following confidence intervals.
(a)
% confidence interval
measurements from a normal
values with the corresponding
values if you were forming
(b)
% confidence interval
(c)
% confidence interval
11) Periodically, the county Water Department tests the drinking water of homeowners for contaminants
such as lead and copper. The lead levels in water specimens collected in 1998 for a sample of 5 residents of
a subdevelopement of the county is shown below.
g/L )
(a) Fill in the following chart to determine the sample mean
and sample standard deviation,
Then,
(b) Determine the critical value,
.
=
(c) Determine the maximal margin of error.
=
(d) Construct a
subdevelopment.
% confidence interval for the mean lead level in water specimans of the
.
12) Justin is interested in buying a digital phone. He visited 10 stores at random and recorded the price of
the particular phone he wants. The sample of prices had a mean of \$389.19 and a standard deviation of
\$10.33.
(a) What critical value
distribution?
should be used for a 95% confidence interval for the mean,
, of the
=
(b) Calculate a 95% confidence interval for the mean price of this model of digital phone:
(Enter the smaller value in the left answer box.)
\$ to \$
13) A random sample of 18 size AA batteries for toys yield a mean of 3.26 hours with standard deviation,
1.42 hours.
(a) Find the critical value,
, for a 99% confidence interval.
=
(b) Find the margin of error for a 99% confidence interval. hour(s).
14) A study is conducted to determine if a newly designed text book is more helpful to learning the
material than the old edition. The mean score on the final exam for a course using the old edition is 75.
Ten randomly selected people who used the new text take the final exam. Their scores are shown in the
table below.
Person A B C D E F G H I J
Test Score 71 86 95 80 90 96 69 88 77 73
Use a
significance level to test the claim that people do better with the new edition. Assume the
standard deviation is 10.2. (Note: You may wish to use statistical software.)
(a) What kind of test should be used?
A. One-Tailed
B. Two-Tailed
C. It does not matter.
(b) The test statistic is (rounded to 2 decimals).
(c) The P-value is
(d) Is there sufficient evidence to support the claim that people do better than 75 on this exam?
A. Yes
B. No
(e) Construct a
% confidence interval for the mean score for students using the new text.

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Tags:
standard deviation

Margin of error

point estimate

gross earnings

correct interpretation

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