In: Statistics and Probability
Chi-Square Test for Independence
Using Chi-Square, we are looking to see if there is a significant difference between what we would expect results to be, and what the actual results were. That is, expected vs. observed. Use alpha = .05
Listed below are data from a survey conducted recently where Males and Females responded to their happiness with their supervisor (this is fictitious data).
Response |
Male |
Female |
Total |
Not at all |
23 |
25 |
48 |
Somewhat |
13 |
22 |
35 |
Very |
26 |
16 |
42 |
Total |
62 |
63 |
125 |
What is your null hypothesis?
What is your alternative hypothesis?
What is the Chi-Square value?
Is there significance evidence that a difference exists between the actual males and female responses in this sample and the expected male/female responses in the population? YES OR NO
The following cross-tabulation have been provided. The row and column total have been calculated and they are shown below:
Male | Female | Total | |
NotAtAll | 23 | 25 | 48 |
Somewhat | 13 | 22 | 35 |
Very | 26 | 16 | 42 |
Total | 62 | 63 | 125 |
Null and Alternative Hypotheses
The following null and alternative hypotheses need to be tested:
H0: The two variables - response and gender are independent
Ha: The two variables - response and gender are dependent
This corresponds to a Chi-Square test of independence.
Test Statistics
The Chi-Squared statistic is computed as follows:
Based on the information provided, the significance level is α=0.05 , the number of degrees of freedom is df=(3−1)×(2−1)=2, so then the rejection region for this test is R={χ2:χ2>5.991}.
Since it is observed that , it is then concluded that the null hypothesis is not rejected. Therefore, there is NOT enough evidence to claim that the two variables are dependent, at the 0.05 significance level.
NO, there is not significance evidence that a difference exists between the actual males and female responses in this sample and the expected male/female responses in the population.
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