In: Statistics and Probability
On its municipal website, the city of Tulsa states that the rate it charges per 5 CCF of residential water is $21.62. How do the residential water rates of other U.S. public utilities compare to Tulsa's rate? The data shown below ($) contains the rate per 5 CCF of residential water for 42 randomly selected U.S. cities.
10.58 | 9.28 | 11.9 | 6.6 | 12.52 | 14.63 | 15.66 |
10.22 | 14.6 | 16.28 | 17.7 | 19.28 | 18.08 | 12.95 |
16.9 | 17.45 | 15.74 | 14.9 | 19.01 | 18.09 | 15 |
18.52 | 16.15 | 26.95 | 22.42 | 22.86 | 21.08 | 23.55 |
19.15 | 23.8 | 19.36 | 23.85 | 27.9 | 27.15 | 27.24 |
27.09 | 24.78 | 37.96 | 26.61 | 39.11 | 29.56 | 41.75 |
(a) Formulate hypotheses that can be used to determine whether the population mean rate per 5 CCF of residential water charged by U.S. public utilities differs from the $21.62 rate charged by Tulsa. (Enter != for ≠ as needed.)
H0:
Ha:
(b) What is the test statistic for your hypothesis test in part (a)? (Round your answer to three decimal places.)
What is the p-value for your hypothesis test in part (a)? (Round your answer to four decimal places.)
(c) At α = 0.05, can your null hypothesis be rejected? What is your conclusion?
- Do not reject H0. The mean rate per 5 CCF of residential water throughout the United States does not differ significantly from the rate per 5 CCF of residential water in Tulsa.
- Do not reject H0. The mean rate per 5 CCF of residential water throughout the United States differs significantly from the rate per 5 CCF of residential water in Tulsa.
- Reject H0. The mean rate per 5 CCF of residential water throughout the United States differs significantly from the rate per 5 CCF of residential water in Tulsa.
- Reject H0. The mean rate per 5 CCF of residential water throughout the United States does not differ significantly from the rate per 5 CCF of residential water in Tulsa.
(d) Repeat the preceding hypothesis test using the critical value approach.
State the null and alternative hypotheses. (Enter != for ≠ as needed.)
H0:
Ha:
Find the value of the test statistic. (Round your answer to three decimal places.)
State the critical values for the rejection rule. Use α = 0.05. (Round your answers to three decimal places. If the test is one-tailed, enter NONE for the unused tail.)
test statistic ≤
test statistic ≥
State your conclusion.
- Do not reject H0. The mean rate per 5 CCF of residential water throughout the United States does not differ significantly from the rate per 5 CCF of residential water in Tulsa.
- Do not reject H0. The mean rate per 5 CCF of residential water throughout the United States differs significantly from the rate per 5 CCF of residential water in Tulsa.
- Reject H0. The mean rate per 5 CCF of residential water throughout the United States differs significantly from the rate per 5 CCF of residential water in Tulsa.
- Reject H0. The mean rate per 5 CCF of residential water throughout the United States does not differ significantly from the rate per 5 CCF of residential water in Tulsa.
Given that,
population mean(u)=21.62
sample mean, x =20.338
standard deviation, s =7.705
number (n)=42
null, Ho: μ=21.62
alternate, H1: μ!=21.62
level of significance, α = 0.05
from standard normal table, two tailed t α/2 =2.02
since our test is two-tailed
reject Ho, if to < -2.02 OR if to > 2.02
we use test statistic (t) = x-u/(s.d/sqrt(n))
to =20.338-21.62/(7.705/sqrt(42))
to =-1.0783
| to | =1.0783
critical value
the value of |t α| with n-1 = 41 d.f is 2.02
we got |to| =1.0783 & | t α | =2.02
make decision
hence value of |to | < | t α | and here we do not reject
Ho
p-value :two tailed ( double the one tail ) - Ha : ( p != -1.0783 )
= 0.2872
hence value of p0.05 < 0.2872,here we do not reject Ho
ANSWERS
---------------
a.
null, Ho: μ=21.62
alternate, H1: μ!=21.62
b.
test statistic: -1.0783
critical value: -2.02 , 2.02
decision: do not reject Ho
c.
p-value: 0.2872
we do not have enough evidence to support the claim that whether
the population mean rate per 5 CCF of residential water charged by
U.S. public utilities differs from the $21.62 rate charged by
Tulsa