Yes an no. Of course, in something like an animal model it can be really hard to control everything, and the result you find could just be 'luck'. On the other

Yes an no. Of course, in something like an animal model it can be really hard to control everything, and the result you find could just be 'luck'. On the other hand, figuring out what variables to control is huge part of science. Say the development of next generation DNA sequencing technologies. People tried a ton of different variables, conditions, reagents, flow cells, etc. And failed and failed. But eventually they controlled the right conditions, optimized the right things, and now the process is done in thousands of labs every day as a routine tool. This is a technology development example, but the same could be said of the conditions needed to make stem cells.