Thank you for your contribution. I find it very fair and sensible. I have my doubts, too, that past, independent occurrences can help with predicting new ones. So, all that remains is probability. But, maybe I’m wrong.
Your view is interesting but I don’t know what an XmR chart is. I’d appreciate it if you could give an example or indicate where I can get one.
Intuitively, I’m inclined to go for Markov chains/model (like somebody else suggested) as I think our problem is similar to predicting the weather. I’m only scratching the surface. My lack of training in maths will make it difficult, though. I must find a “hands-on” example. If I make any progress, I'll keep everybody posted.