Screening Replicated factorial DOE - Half normal plot - null space terms?
I create a 2x2 full factorial DOE, with 1 replication. Sorting my data from right to left, my responses are 10, 11, 20, 19, 30, 28, 37, 40.
I run the screening script and a half normal plot is created - so far so good. But there are 7 points in the half normal plot, but just 3 effects (2 x main effects and 1 x 2 factor interaction). One of the null terms 'Null7' is even highlighted as significant.
F...