Principle (Length of Line): For a line where all the processing times are identical at all the stations, the defect rate is increasing in the number of the stations in the line.
Motivation
As the length of the line increases the total number of opportunities to create a defect (i.e., not finish a task during the cycle time) also increases. To see this, suppose that each station has a probability p of producing a defect. Then the probabilty of a good part from an n station line is (1-p)n, which is obviously decreasing in n. Hence, the defect rate increases in n.