Michelson-Gale-Pearson Experiment

From a work titled The Sagnac and Michelson-Gale-Pearson Experiments (Archive) by Dr. Paulo N. Correa we read on p.5:

Essentially the tests saw wild results. There was almost no change to light's velocity in one test, yet a lot of change in another test. It is perplexing that the rotation of the earth would start and stop when tested at different times. Only through the statistics was it claimed that the experiment saw the rotation of the earth. As stated, the inconsistent results were ambiguous in nature and could offer no evidence of the shift in the phase of the light beams.

Other Resources
How to Lie with Statistics by Darrell Huff (Psychology Today Article)