In: Statistics and Probability
The Wall Street Journal Corporate Perceptions Study 2011 surveyed readers and asked how each rated the quality of management and the reputation of the company for over 250 worldwide corporations. Both the quality of management and the reputation of the company were rated on an excellent, good, and fair categorical scale. Assume the sample data for 200 respondents below applies to this study.
Quality of Management | Reputation of Company | ||
---|---|---|---|
Excellent | Good | Fair | |
Excellent | 41 | 25 | 5 |
Good | 34 | 35 | 10 |
Fair | 25 | 10 | 15 |
1)Use a 0.05 level of significance and test for independence of the quality of management and the reputation of the company.
-State the null and alternative hypotheses.
- Find the value of the test statistic
-Find the p-value
-State your conclusion.;
a)Reject H0. We conclude that the rating for the quality of management is independent of the rating for the reputation of the company.
b)Reject H0. We conclude that the rating for the quality of management is not independent of the rating for the reputation of the company.
c)Do not reject H0. We cannot conclude that the ratings for the quality of management and the reputation of the company are not independent.
d)Do not reject H0. We cannot conclude that the rating for the quality of management is independent of the rating of the reputation of the company.
2)If there is a dependence or association between the two ratings, discuss and use probabilities to justify your answer.
For companies with an excellent reputation, the largest column probability corresponds to ---Select--- excellent good fair management quality. For companies with a good reputation, the largest column probability corresponds to ---Select--- excellent good fair management quality. For companies with a fair reputation, the largest column probability corresponds to ---Select--- excellent good fair management quality. Since these highest probabilities correspond to ---Select--- the same different ratings of quality of management and reputation, the two ratings are
Solution :
Expected Table :
Quality of Management |
Reputation of company | |||
Excellent | Good | Fair | ||
Excellent | (71 * 100) / 200 = 35.5 | (71 * 70) / 200 = 24.85 | (71 * 30) / 200 = 10.65 | 71 |
Good | (79 * 100) / 200 = 39.5 | (79 * 70) / 200 = 27.65 | (79 * 30) / 200 = 11.85 | 79 |
Fair | (50 * 100) / 200 = 25 | (50 * 70) / 200 = 17.5 | (50 * 30) / 200 = 7.5 | 50 |
Total | 100 | 70 | 30 | 200 |
Percentage | Oi | Ei | ( Oi - Ei ) | ( Oi - Ei )2 | ( Oi - Ei )2 / Ei |
41 | 35.5 | 5.5 | 30.25 | 0.8521 | |
25 | 24.85 | 0.15 | 0.0225 | 0.0009 | |
5 | 10.65 | -5.65 | 31.9225 | 2.9974 | |
34 | 39.5 | -5.5 | 30.25 | 0.7658 | |
35 | 27.65 | 7.35 | 54.0225 | 1.9538 | |
10 | 11.85 | -1.85 | 3.4225 | 0.2888 | |
25 | 25 | 0 | 0 | 0 | |
10 | 17.5 | -7.5 | 56.25 | 3.2143 | |
15 | 7.5 | 7.5 | 56.25 | 7.5 | |
Total | 200 | 200 | 0 | 262.39 | 17.5731 |
To Test :-
Hypothesis :-
H0 :- Quality of management and reputation of company are independent
H1 :- Quality of management and reputation of company are dependent
Test Statistic :-
X2 = Σ (Oi - Ei )2 / Ei
X2 = 17.573
Test Criteria :-
Reject null hypothesis if X2 > X2(α, (r-1)(c-1))
Critical value X2(0.05, (3-1) (3-1)) = X2(0.05,4) = 9.488 ( From
chi square table )
Since, 17.5731 > 9.488
Conclusion = Reject null hypothesis
Decision based on P value
P (X2 > 17.5731) = 0.0015
Reject null hypothesis if P value < α = 0.05
P value = 0.0015 < 0.05, hence we reject null hypothesis
Conclusion = Reject null hypothesis
Option B is correct.
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