A company claims that the mean monthly residential electricity consumption in a certain region is more than 860 ​kiloWatt-hours (kWh). You want to test this claim. You find that a random sample of 63 residential customers has a mean monthly consumption of 880 kWh. Assume the population standard deviation is 120 kWh. At α=0.01​, can you support the​ claim? Complete parts​ (a) through​ (e). ​(a) Identify H0 and Ha. Choose the correct answer below. A. H0​: μ>880 ​(claim) Ha​: μ≤880 B. H0​: μ>860 ​(claim) Ha​: μ≤860 C. H0​: μ=860 ​(claim) Ha​: μ≠860 D. H0​: μ≤860 Ha​: μ>860 ​(claim) E. H0​: μ≤880 Ha​: μ>880 ​(claim) F. H0​: μ=880 Ha​: μ≠880 ​(claim) ​(b) Find the critical​ value(s) and identify the rejection​ region(s). Select the correct choice below and fill in the answer box within your choice. Use technology. ​(Round to two decimal places as​ needed.) A. The critical value is nothing. B. The critical values are ±nothing. Identify the rejection​ region(s). Select the correct choice below. A. The rejection region is z<2.33. B. The rejection regions are z<−2.33 and z>2.33. C. The rejection region is z>2.33. ​(c) Find the standardized test statistic. Use technology. The standardized test statistic is z=nothing. ​(Round to two decimal places as​ needed.) ​(d) Decide whether to reject or fail to reject the null hypothesis. A. Fail to reject H0 because the standardized test statistic is not in the rejection region. B. Reject H0 because the standardized test statistic is not in the rejection region. C. Fail to reject H0 because the standardized test statistic is in the rejection region. D. Reject H0 because the standardized test statistic is in the rejection region. ​(e) Interpret the decision in the context of the original claim. At the 1​% significance​ level, there ▼ is notis not isis enough evidence to ▼ reject support the claim that the mean monthly residential electricity consumption in a certain region ▼ is different from is greater than is less than nothing kWh. Click to select your answer(s).

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Author:Amos Gilat
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A company claims that the mean monthly residential electricity consumption in a certain region is more than
860
​kiloWatt-hours (kWh). You want to test this claim. You find that a random sample of
63
residential customers has a mean monthly consumption of
880
kWh. Assume the population standard deviation is
120
kWh. At
α=0.01​,
can you support the​ claim? Complete parts​ (a) through​ (e).
​(a) Identify
H0
and
Ha.
Choose the correct answer below.
 
 
A.
H0​:
μ>880
​(claim)
Ha​:
μ≤880
 
B.
H0​:
μ>860
​(claim)
Ha​:
μ≤860
 
C.
H0​:
μ=860
​(claim)
Ha​:
μ≠860
 
D.
H0​:
μ≤860
Ha​:
μ>860
​(claim)
 
E.
H0​:
μ≤880
Ha​:
μ>880
​(claim)
 
F.
H0​:
μ=880
Ha​:
μ≠880
​(claim)
​(b) Find the critical​ value(s) and identify the rejection​ region(s). Select the correct choice below and fill in the answer box within your choice. Use technology.
 
​(Round to two decimal places as​ needed.)
 
A.
The critical value is
nothing.
 
B.
The critical values are
±nothing.
Identify the rejection​ region(s). Select the correct choice below.
 
 
A.
The rejection region is
z<2.33.
 
B.
The rejection regions are
z<−2.33
and
z>2.33.
 
C.
The rejection region is
z>2.33.
​(c) Find the standardized test statistic. Use technology.
 
The standardized test statistic is
z=nothing.
​(Round to two decimal places as​ needed.)
​(d) Decide whether to reject or fail to reject the null hypothesis.
 
 
A.
Fail to reject
H0
because the standardized test statistic
is not
in the rejection region.
 
B.
Reject
H0
because the standardized test statistic
is not
in the rejection region.
 
C.
Fail to reject
H0
because the standardized test statistic
is
in the rejection region.
 
D.
Reject
H0
because the standardized test statistic
is
in the rejection region.
​(e) Interpret the decision in the context of the original claim.
 
At the
1​%
significance​ level, there
 
is notis not
isis
enough evidence to
 
reject
support
the claim that the mean monthly residential electricity consumption in a certain region
 
is different from
is greater than
is less than
nothing
kWh.
 
Click to select your answer(s).
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