Compatibility Test
1. **State the problem:** We want to test if the responses for compatibility levels between Microsoft and Linux operating systems differ significantly at a 5% significance level.
2. **Set hypotheses:**
- Null hypothesis $H_0$: The distribution of compatibility responses is the same for Microsoft and Linux.
- Alternative hypothesis $H_a$: The distributions differ.
3. **Data:**
| Compatibility Level | Microsoft | Linux |
|---------------------|-----------|-------|
| High | 96 | 56 |
| Moderate | 90 | 84 |
| Low | 27 | 67 |
4. **Calculate totals:**
- Microsoft total: $96 + 90 + 27 = 213$
- Linux total: $56 + 84 + 67 = 207$
- Grand total: $213 + 207 = 420$
5. **Calculate expected counts under $H_0$:**
For each cell, expected count = (row total * column total) / grand total.
Column totals:
- High: $96 + 56 = 152$
- Moderate: $90 + 84 = 174$
- Low: $27 + 67 = 94$
Expected counts for Microsoft:
- High: $\frac{213 \times 152}{420} = 77.14$
- Moderate: $\frac{213 \times 174}{420} = 88.29$
- Low: $\frac{213 \times 94}{420} = 47.57$
Expected counts for Linux:
- High: $\frac{207 \times 152}{420} = 74.86$
- Moderate: $\frac{207 \times 174}{420} = 85.71$
- Low: $\frac{207 \times 94}{420} = 46.43$
6. **Compute Chi-square statistic:**
$$\chi^2 = \sum \frac{(O - E)^2}{E}$$
Where $O$ is observed and $E$ is expected.
Calculations:
- Microsoft High: $\frac{(96 - 77.14)^2}{77.14} = 4.56$
- Microsoft Moderate: $\frac{(90 - 88.29)^2}{88.29} = 0.03$
- Microsoft Low: $\frac{(27 - 47.57)^2}{47.57} = 9.02$
- Linux High: $\frac{(56 - 74.86)^2}{74.86} = 4.56$
- Linux Moderate: $\frac{(84 - 85.71)^2}{85.71} = 0.03$
- Linux Low: $\frac{(67 - 46.43)^2}{46.43} = 9.02$
Sum:
$$\chi^2 = 4.56 + 0.03 + 9.02 + 4.56 + 0.03 + 9.02 = 27.22$$
7. **Degrees of freedom:**
$df = (rows - 1)(columns - 1) = (2-1)(3-1) = 2$
8. **Critical value at 5% significance and 2 df:**
$\chi^2_{critical} = 5.991$
9. **Decision:**
Since $27.22 > 5.991$, we reject the null hypothesis.
10. **Conclusion:**
There is sufficient evidence at the 5% significance level to conclude that the compatibility responses differ between Microsoft and Linux operating systems.