Question

Periodically, a town water department tests the the drinking water of homeowners for contaminants such as lead. The lead levels in water specimens collected for a sample of 10 residents of the town had a mean of 2.8 mg/L and a standard deviation of 2.7 mg/L. Complete parts a through c.

**a.** Construct a 90% confidence interval for the
mean lead level in water specimens from the town.

**b**. Interpret the interval in terms of this
application. Choose the correct answer below.

A. The water department can be 10% confident that the mean lead level in drinking water for all residents in the town is within this interval.

B. The water department can be 90% confident that the mean lead level in drinking water for all residents in the town is 2.8mg/L.

C. The water department can be 90% confident that the mean lead level in drinking water for all residents in the town is within this interval.

D. The water department can be 90% confident that the mean lead level in drinking water for all residents in the town is outside this interval.

E. The water department is confident that 90% of the mean lead level in drinking water for all residents in the town is described by this interval.

**c.**The phrase "90% confidence interval" means
that if many intervals were constructed using the same methods and
the same ____________________ then____% of those intervals would
contain the true _________________.

Answer #1

Periodically, a town water department tests the the drinking
water of homeowners for contaminants such as lead. The lead levels
in water specimens collected for a sample of 10 residents of the
town had a mean of 3.1 mg/L and a standard deviation of 1.6 mg/L.
Complete parts a through c.
a.Construct a 90% confidence interval for the mean lead level
in water specimens from the town.
left parenthesis nothing comma nothing right parenthesis,
(Round to three decimal places as...

Periodically, a town water department tests the the drinking
water of homeowners for contaminants such as lead. The lead levels
in water specimens collected for a sample of 10 residents of the
town had a mean of 3.2 ?mg/L and a standard deviation of 2.9 ?mg/L.
Complete parts a through c.
a. Construct a 90?%confidence interval for the
mean lead level in water specimens from the town.

The Busy Town drinking water treatment plant recently changed
coagulant aid from alum
to ferrous sulfate (FeSO4·7H2O) for TSS removal. The raw water
contains 7 mg/L of TSS.
Ferrous sulfate coagulation proceeds as follows:
FeSO4·7H2O + 2 Ca(HCO3-) + 1⁄2O2 -> 2Fe(OH)3 (s) ↓ + 2CaSO4 +
13H2O
If an optimum dose of 30 mg/L of ferrous sulfate is required to
remove 90% of the TSS, calculate the mass of residuals (mg/L)
generated in this process.

You are given the sample mean and the population standard
deviation. Use this information to construct the 90% and 95%
confidence intervals for the population mean. Interpret the results
and compare the widths of the confidence intervals. From a random
sample of 33 business days, the mean closing price of a certain
stock was $111.13. Assume the population standard deviation is
$10.41. The 90% confidence interval is ( nothing, nothing).
(Round to two decimal places as needed.) The 95% confidence...

1. the county health
department has concerns about the chlorine level at a local water
park. the health department tests the water monday with readings of
4 mg out of 100 ml. on thursday when the water is tested, the
health dept. gets readings of 5 mg out of 120 ml. assume that the
samples are independent and that they have been randomly selected.
construct a 90% confidence interval for the difference in the
proportions of water samples on monday...

In a certain country, pesticide T is used for controlling
insects that are harmful to crops. According
to standards set by government, drinking water wells with
level of pesticide T above 1 part per billion
are considered contaminated. A study has been conducted by the
Environmental Protection
Department (EPD) which has selected a random sample of 250
wells and tested them, and it is found
that 50 wells are contaminated.
(a) Construct a 90% confidence interval for the true
proportion...

In a recent household telephone survey of 2,870 adults in a
certain? country, 28?% reported that they own at least one gun. The
researchers want to estimate the true percentage of adults in that
country that own at least one gun. Complete parts
a through f below.
a. Identify the population of interest to the
researchers. Choose the correct answer below.
A.The set of adults that responded to the survey
B.The set of guns in the country
C.The set of...

(1 point)
Weights of 10 red and 36 brown randomly chosen M{\&}M plain
candies are listed below.
Red:
0.9080.9090.9070.920.9360.8980.8980.8740.9130.9240.9080.9070.9360.8980.9130.9090.920.8980.8740.924
Brown:
0.9090.9150.9550.9140.9310.9090.9050.930.8570.8770.9660.9020.920.9040.8660.8710.8720.9280.9880.920.8580.8980.9360.9210.9850.8750.9290.90.9230.8610.8670.8760.9020.8970.9180.9130.9090.9050.920.9880.9850.8670.9150.930.9040.920.8750.8760.9550.8570.8660.8580.9290.9020.9140.8770.8710.8980.90.8970.9310.9660.8720.9360.9230.9180.9090.9020.9280.9210.8610.913
1. To construct a 95% confidence interval
for the mean weight of red M{\&}M plain candies, you have to
use
A. The t distribution with 11 degrees of
freedom
B. The normal distribution
C. The t distribution with 9 degrees of
freedom
D. The t distribution with 10 degrees of
freedom
E. None of the above
2. A 95% confidence interval...

Let x be a random variable that represents micrograms
of lead per liter of water (µg/L). An industrial plant discharges
water into a creek. The Environmental Protection Agency (EPA) has
studied the discharged water and found x to have a normal
distribution, with
σ = 0.7 µg/L.
† Note: For degrees of freedom d.f. not in the
Student's t table, use the closest d.f. that is smaller.
In some situations, this choice of d.f. may increase the
P-value a small...

1) The weekly oral dose of anabolic steroids was measured on a
sample of 20 body builders. A 95% confidence interval
estimatefortheaverageweeklyoraldoseofanabolicsteroidsobtainedfromtheseresultswas152mgto194
mg. (The margin of error is 21 mg.) Identify which one of the
following interpretations is correct.
a) 95% of all body builders use between 152 mg and 194 mg of
anabolic steroids per week.
b) There is a 0.95 probability that the average weekly dose of
anabolic steroids used by body builders is between
152 mgand194mg.
c)...

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