Hi, I came through this post while googling for the same thing. Taguchi design L9 is a saturated model, if you did only 9 experiments. In that case, you can eliminate one or two less significant terms from the model. It is called 'pooling'. When you did one set of repetitions you will have 9 more equations for estimating statistics. DOF of error/residual will be 9. With that you can calculate F and P values. Refer the following book. It's simple and easy to understand.

**Design of Experiments Using The Taguchi Approach: 16 Steps to Product and Process Improvement**