1. **State the problem:**
A sociologist wants to test if the distribution of preferred study methods among college students is equally likely using a Chi-square Goodness of Fit test with significance level $\alpha = 0.05$.
2. **Hypotheses:**
- Null hypothesis $H_0$: The distribution of preferred study methods is uniform (all methods equally likely).
- Alternative hypothesis $H_a$: The distribution of preferred study methods is not uniform.
3. **Expected probabilities:**
Since there are 6 study methods, each is expected to have probability $\frac{1}{6}$.
4. **Observed values:**
Roll a six-sided die 30 times to simulate observed counts for each method.
Assume the following observed counts (example):
- Group Study (1): $O_1 = 5$
- Solo Study (2): $O_2 = 4$
- Online Tutoring (3): $O_3 = 6$
- In-Person Tutoring (4): $O_4 = 7$
- Library Study (5): $O_5 = 3$
- Peer Teaching (6): $O_6 = 5$
5. **Expected counts:**
$$E_i = n \times p_i = 30 \times \frac{1}{6} = 5$$
for each category $i$.
6. **Create observed vs expected table:**
| Method | Observed ($O_i$) | Expected ($E_i$) |
|--------|------------------|------------------|
| 1 | 5 | 5 |
| 2 | 4 | 5 |
| 3 | 6 | 5 |
| 4 | 7 | 5 |
| 5 | 3 | 5 |
| 6 | 5 | 5 |
7. **Calculate Chi-square test statistic:**
$$\chi^2 = \sum_{i=1}^6 \frac{(O_i - E_i)^2}{E_i} = \frac{(5-5)^2}{5} + \frac{(4-5)^2}{5} + \frac{(6-5)^2}{5} + \frac{(7-5)^2}{5} + \frac{(3-5)^2}{5} + \frac{(5-5)^2}{5}$$
$$= 0 + \frac{1}{5} + \frac{1}{5} + \frac{4}{5} + \frac{4}{5} + 0 = \frac{10}{5} = 2$$
8. **Degrees of freedom:**
$$df = k - 1 = 6 - 1 = 5$$
9. **Find p-value:**
Using Chi-square distribution with $df=5$, $\chi^2=2$ gives a p-value approximately $0.85$ (high p-value).
10. **Conclusion:**
Since $p = 0.85 > \alpha = 0.05$, we fail to reject the null hypothesis.
**Interpretation:** There is not enough evidence to conclude that the preferred study methods are distributed unequally. The sociologist can say students use all study methods equally based on this test.
Chi Square Goodness
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