In: Statistics and Probability
A random survey of 85 women who were victims of violence found that 28 were attacked by relatives. A random survey of 46 men found that 5 were attacked by relatives. At =α0.10, can it be shown that the percentage of women who were attacked by relatives is greater than the percentage of men who were attacked by relatives? Use p1 for the proportion of women who were attacked by relatives. Use the P-value method with tables.
A) Compute the test.
B) Find the P value.
C) Reject or do not reject the null hypothesis.
D) There is or is not enough evidence to support the claim?
Solution :
For sample 1, we have that the sample size is N1=85, the number of favorable cases is X1=28, so then the sample proportion is
For sample 2, we have that the sample size is N2=46, the number of favorable cases is X2=5, so then the sample proportion is
The value of the pooled proportion is computed as
Also, the given significance level is α=0.10.
(1) Null and Alternative Hypotheses
The following null and alternative hypotheses need to be tested:
Ho: p1=p2
Ha: p1>p2
This corresponds to a right-tailed test, for which a z-test for two population proportions needs to be conducted.
(2) Rejection Region
Based on the information provided, the significance level is α=0.10, and the critical value for a right-tailed test is zc=1.28.
The rejection region for this right-tailed test is R={z:z>1.28}
(3) Test Statistics
The z-statistic is computed as follows:
The p-value is p=P(Z>2.778)=0.0027
(4) The decision about the null hypothesis
Since it is observed that z=2.778>zc=1.28, it is then concluded that the null hypothesis is rejected.
Using the P-value approach: The p-value is p=0.0027, and since p=0.0027<0.10, it is concluded that the null hypothesis is rejected.
(5) Conclusion
It is concluded that the null hypothesis Ho isrejected. Therefore, there is enough evidence to claim that population proportion p1 is greater than p2, at the 0.10 significance level
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