Almost 50 years after the assassination of John F. Kennedy, a poll shows that most Americans disagree with the government's conclusions about the killing. The Warren Commission found that Lee Harvey Oswald acted alone when he shot Kennedy, but many Americans are not so sure. Do you think that we know all the facts about the assassination of President John F. Kennedy or do you think there was a cover-up? Here are the results from a poll of 900 registered voters nationwide.
We Know All the Facts | There Was a Cover-Up | Not Sure | |
---|---|---|---|
Democrats | 42 | 309 | 32 |
Republicans | 64 | 247 | 47 |
Independents | 20 | 115 | 24 |
(a) Do these data provide sufficient evidence to conclude that there is a difference in voters' opinions about a possible cover-up depending on the political affiliation of the voter? Test using α = 0.05.
Find the test statistic. (Round your answer to three decimal places.)
Χ^{2} =
We would be first computing the expected value for each cell
here as:
E_{i} = (Sum of column i)*(Sum of row i) / Grand Total
Grand Total = 900 here is the total frequency.
The chi square test statistic contribution for each cell now is computed here as:
These are computed as:
Note that the circular bracket here contains the expected frequency while the square bracket contains the chi square test statistic contribution here.
Now the test statistic is computed by summing up all the contributions here as:
Therefore 16.041 is the required test statistic value here.
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