[nerdponx]

3x as many emergencies per employee (not total, per employee) would be at least moderately alarming even if the numbers were 0.003 accidents per employee at Tesla and 0.001 accidents per employee at Audi.

I wouldn't get too hung up on statistical significance here. Whenever someone brings up statistical significance, I always like to ask: "significant with respect to what? by what standard?"

However it might be interesting to consider whether 3x is normal for all new production facilities. But that's a separate question.

[3rd3]

Even though p-values can be hacked, they are very useful when they aren't. At p = 0.1 I'd ignore the finding because there would be a 10% chance it was explained by random chance. p = 0.01 would pique my interest. p < 0.001 I'd accept it as true, but I'd still watch out for systematic biases such as comparing new to old factories.

[nerdponx]

Right, if you're at the point of constructing some kind of principled estimate of variation in the data then I think you have a pass to at least talk about "significance". But in that case I'm sure you're aware that this requires a particular hypothesis test in mind, not just an abstract notion of "significance", and that p-values interpreted as "strength of evidence" are problematic.