Process design

Comparing traditional approaches to experimental design

The traditional approach taken to develop a new process is One Factor at a Time (OFAT) (Figure 1).  Experimental design on the other hand is a structured set of tests of a process to investigate potentially significant factors that helps to establish cause and effect relationship on the output (Figure 2)  The advantages and disadvantages of both approaches are discussed in Table 1 and Table 2 below.

Figure 1: One Factor at a Time (OFAT) approach
Figure 2: Experimental Deisgn (DoE) approach

Table 1: Advantages and disadvantages of the OFAT approach

Advantages

Disadvantages

Widely taught

Limited coverage of the experimental space

Straightforward

May miss the optimal solution

 

Fails to identify interactions

 

Inefficient use of resources

Table 2: Advantages and disadvantages of the DoE approach

Advantages

Disadvantages

Systematic: Thorough coverage of experimental “space”

Minimum entry of ca. 10 experiments

Efficient: Able to establish solution with minimal resource

You may have to run experiments that you anticipate will “fail”