Option C is correct.
The 437 county residents were a random sample of all county residents.
a) If p is the proportion of Hispanics in the county,
The null hypothesis is represented as
H₀: p = 0.16
The alternative hypothesis is represented as
Hₐ: p ≠ 0.35
b) The model of the test is two-tailled, one-proportion test. And it satisfies all of the required conditions for an hypothesis test.
c) The sketch of the region of acceptance is presented in the attached image to this answer. (z < -4.09 and z > 4.09).
Test statistic = -4.09
p-value = 0.000043
d) We can conclude that the proportion of the county that are Hispanics is different from the proportion of the country that are Hispanics.
Step-by-step explanation:
According to the question, it was clearly stated that the 437 county residents are a random sample of the residents in the county, hence, it is evident that option C is the right statement.
a) For hypothesis testing, the first thing to define is the null and alternative hypothesis.
The null hypothesis plays the devil's advocate and usually takes the form of the opposite of the theory to be tested. It usually contains the signs =, ≤ and ≥ depending on the directions of the test.
While, the alternative hypothesis usually confirms the the theory being tested by the experimental setup. It usually contains the signs ≠, < and > depending on the directions of the test.
For this question, the county supervisor wants to check if proportion of the county that are Hispanics is different from the proportion of the whole nation that are Hispanics. (0.16).
Hence, the null hypothesis is that there isn't enough evidence to conclude that the proportion of the county that are Hispanics is different from the proportion of the whole nation that are Hispanics. That is, there is no significant difference between the proportion of the county that are Hispanics and the proportion of the whole nation that are Hispanics. (0.16).
The alternative hypothesis will now be that enough evidence to conclude that the proportion of the county that are Hispanics is different from the proportion of the whole nation that are Hispanics (0.16).
Mathematically,
The null hypothesis is represented as
H₀: p = 0.16
The alternative hypothesis is represented as
Hₐ: p ≠ 0.16
b) To do this test, we will use the z-distribution because although, no information on the population standard deviation is known, the sample size is large enough.
Hence, the model of this test is two-tailled, one-proportion test.
And the major conditions for an hypothesis test is that
- The sample must be a random sample extracted from the population, with each variable in the sample independent from one another. This is already clearly given in the question.
- The sample must be a normal distribution sample or approximate a normal distribution.
The conditions to check this is that
np ≥ 10
and
np(1-p) ≥ 10
p = sample proportion = (44/437) = 0.101
np = 437×0.101 = 44 ≥ 10
np(1-p) = 437×0.101×(1-0.101) = 39.7 ≥ 10
The two conditions are satisfied, hence, we can conclude that this distribution at least approximates a normal distribution.
c) So, we compute the t-test statistic
z = (x - μ)/σₓ
x = sample proportion = 0.101
μ = p₀ = The proportion we are comparing against = 0.16
σₓ = standard error = √[p(1-p)/n]
where n = Sample size = 437
σₓ = √[0.101×0.899/437] = 0.0144145066 = 0.0144
z = (0.101 - 0.16) ÷ 0.0144
z = -4.093 = -4.09
checking the tables for the p-value of this z-statistic
Degree of freedom = df = n - 1 = 437 - 1 = 436
Significance level = 0.05 (when the significance level isn't stated, 0.05 is used)
The hypothesis test uses a two-tailed condition because we're testing in both directions (greater than or less than).
p-value (for z = -4.09, at 0.05 significance level, df = 436, with a two tailed condition) = 0.000043
The sketch of the region of acceptance is presented in the attached image to this answer. (z < -4.09 and z > 4.09).
d) The interpretation of p-values is that
When the (p-value > significance level), we fail to reject the null hypothesis and when the (p-value < significance level), we reject the null hypothesis and accept the alternative hypothesis.
So, for this question, significance level = 0.05
p-value = 0.000043
0.000043 < 0.05
Hence,
p-value < significance level
This means that we reject the null hypothesis, accept the alternative hypothesis & say that there is enough evidence to conclude that the proportion of the county that are Hispanics is different from the proportion of the whole nation that are Hispanics.
Hope this Helps!!!
