【正文】 cause you want to minimize the cost of obtaining information. ? What is your knowledge of the process? What do you know about important factors and how they work together (interactions)? How close to optimum are you currently running? What is the operating range of each factor? Once you define your goal, your environment and your knowledge, you can choose an adequate experimental design. Four questions to determine the type of design EN/FAD 109 0015 169。 Ola Johansson, 1999 Ericsson Quality Management Institute DOE Objectives ? To determine those variables / predictors (time, temperature etc) that are most influential on the response ? To assess the best settings / levels of those significant variables that result in a response near a desired value maximum / minimum / nominal. ? To assess the best settings / levels of those significant variables that miminise variability in the response. ? To assess the best settings / levels of those significant variables that reduce the effect / impact of ?noise? nuisance variables EN/FAD 109 0015 169。 Conduct Trials Analyse amp。 Ola Johansson, 1999 Ericsson Quality Management Institute A Two Level Factorial Design ? Effect of pressure is difference in mean response between runs where it is at plus (high) level and minus (low) level ? Effect is units but do not know if this is significant ? Analysing the design calculating the “effect” of changing the factors : level minus (low) to level plus (high) Std Order 1 2 3 4 5 6 7 8 Run Order 4 7 3 1 5 8 6 2 Pressure 55 70+ 55 70+ 55 70+ 55 70+ Heat Med Med High + High + Med Med High + High + Time 6 6 6 6 8+ 8+ 8+ 8+ Response Effect of pressure = + + + + + + = 4 4 To pare the mean values where pressure is high and low EN/FAD 109 0015 169。 Ola Johansson, 1999 Ericsson Quality Management Institute Replicated Factorial Designs with Text Variables ? Problem : You want to study the effect of oil viscosity, temperature, and a special additive on engine wear. ? Procedure: You are looking for the treatment that produces the least wear. You replicate the experiments so you will have two runs for each treatment and will be able to test all possible interactions. All experiments can be run in a single day. ? Factor levels : Viscosity (30,40)。M Nuisance variables Control variables Constant variables Independent variables Influential Measurable Controllable Low B High B Low A High A Response Low B High B Low A High A Response Interaction No interaction Low A High A 5 6 4 3 Low A High A 5 4 3 Low B High B Interactions Control variables Trial number D of E Array Qualitative amp。 Ola Johansson, 1999 Ericsson Quality Management Institute Planning for Success Structured Problem Solving List the Problems Select the Problem Analyse the Problem Decide the Facts Gather Data Interpret Data Devise Solution Present Findings Implement Monitor Action Evaluation amp。 Additive ( A, B)。 Ola Johansson, 1999 Ericsson Quality Management Institute A Two Level Factorial Design ? Coefficients determined by dividing effect by 2 ? Constant found by the mean of all responses Pressure Heat Time Pr*He Pr*Ti He*Ti Pr*He*Ti +