Good point. I was going to say that the motion of the ball is random, but of course it depends on the time scale involved.
Let us use the language of a mathematician to describe the motion.
Let us assume that the ball is launched at t=0, and t, representing time, goes upward. i.e. t=1 second is one second after the ball is launched.
Let us also assume that the maximum amount of time the ball spends in the pinball machine before draining is 10 minutes. This value is determined using empirical observation.
The "motion of the ball" can be represented by describing the position of the ball at time t. We'll call that p(t).
For t<10 minutes, p(t) is a random variable. For t>10 minutes, p(t) is not a random variable.
So, for a mathematician, the motion of the ball may be considered random, or non-random, depending on exactly what question related to motion he wants to answer.
Nor should you. You should use the best language possible to describe to your target audience the phenomena in question. If you happen to be describing evolution at the time, that might mean "random" or it might be "nonrandom", depending on exactly which aspect of evolution you are describing, and to whom you are describing it.
The article from the OP did a real disservice, in my opinion. It's title somehow implied that this study confirms Darwin's theory. Is that correct? I certainly hope not, because the finding of the study was not what the article claimed. The article found that most traits evolved deterministically, but some traits evolved stochastically. If one or the other finding would disprove Darwin's theory, then the theory would have been disproved.
Fortunately, we don't have to rewrite biology textbooks just yet. Darwin's theory was not being tested in this study. This study was simply refining a description of the mechanism involved. If you were to read the journal article, you would find no reference at all to any question about verifying evolutionary theory, because that wasn't under study. That question has been settled long ago. The biologists are just fine tuning their understanding of the details at this point.
Meanwhile, the paper defined the terms "stochastic" and "deterministic" in a particular way, and then tried to determine whether traits evolved stochastically or deterministically. We could argue with their definitions if we were so inclined, but that would be foolish. The words have ambiguity in their definitions, but the paper's authors defined exactly what definitions they were using, and how they were applying them to their specific aspect of evolution. Therefore, whether or not we like the way they defined their terms, those terms were defined precisely within the paper, and anyone reading the paper can see what they meant, and learn something about evolution from the paper.
