Factorial Designs
1. **Problem Statement:** Analyze the factorial experiment data for yield based on pressure and temperature with three levels each and two replicates.
2. **Method:** Use two-factor factorial ANOVA to analyze main effects and interaction effects.
3. **Formula:** Total variation = Variation due to Pressure + Variation due to Temperature + Interaction + Error.
4. **Steps:**
- Calculate means for each factor level and overall mean.
- Compute sum of squares for Pressure (SS_P), Temperature (SS_T), Interaction (SS_PT), and Error (SS_E).
- Calculate degrees of freedom for each source.
- Compute mean squares (MS) by dividing SS by respective df.
- Calculate F-statistics: $F_P = \frac{MS_P}{MS_E}$, $F_T = \frac{MS_T}{MS_E}$, $F_{PT} = \frac{MS_{PT}}{MS_E}$.
- Compare F-values with critical F at $\alpha=0.05$ to determine significance.
5. **Interpretation:** Significant factors or interaction indicate influence on yield.
6. **Operating Conditions:** Choose pressure and temperature levels with highest mean yield and no significant negative interaction.
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7. **Question 2:** Analyze influence of temperature and glass type on oscilloscope tube response.
8. **Method:** Two-factor factorial ANOVA with interaction.
9. **Steps:**
- Calculate means and sum of squares for glass type, temperature, interaction, and error.
- Compute F-statistics and compare with critical F at $\alpha=0.05$.
- Determine if interaction or main effects are significant.
10. **Conclusion:** Significant interaction means effect of one factor depends on the other; otherwise, main effects are interpreted.
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11. **Question 3:** Analyze two-factor factorial data and test for nonadditivity.
12. **Method:** Use Tukey's test for nonadditivity.
13. **Steps:**
- Fit additive model and calculate residuals.
- Compute test statistic for nonadditivity.
- Compare with critical value at $\alpha=0.05$.
14. **Conclusion:** If nonadditivity is significant, interaction or nonlinear effects exist.
**Final answers:**
- Use factorial ANOVA for Questions 1 and 2 to identify significant factors and interactions.
- Use Tukey's test for nonadditivity in Question 3.
- Operate process at factor levels with highest yield and no significant negative interactions.