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by cptvideo2 3737 days ago
>take the Monty Hall problem

It amazing how many people still don’t get the Monty Hall problem. Its lesson is that the probabilities do NOT change – until we make a choice!. That’s why it’s better to switch once we see the goat behind door 1. The probability of our having made a good choice, initially (1 in 3), has NOT changed even though there are now only two ‘choices’. But they are not REALLY choices because we’ve ALREADY chosen. The probability can only change if we make a NEW choice, because the ‘probability’ that we’re discussing is the probability that our choice, at the time it was made, would produce a result that we wanted. The iPhone 5 is clearly no less secure now than it was then. But we can switch.

2 comments

The iPhone 5 is now less secure because attackers now know that there is a vulnerability, and they will find it. If, previously, they had thought there wasn't a vulnerability, they might have invested fewer resources in hacking it. That is now no longer the case.

Increasing the number of people who will find exploits on a device, will reduce the security of that device.

Put another way - a platform that no (talented) engineers are attempting to find exploits for is more secure than the same platform if many talented engineers put their time into finding exploits for it.

It's much easier to understand when you realize that Monty never reveals that one of the closed doors contained the car.

That asymmetry of action leads to the asymmetry of probabilities; your initial choice constrained his choices when he takes action.

Well, Monty doesn't know (or care about) your choice. He's 'constrained' by the fact that his 'probability' is 100%: he knows where the goats and car are.
What? Of course his action is based on your choice.

If a has the car and b and c have goats, and you pick b, he opens c. And if you pick c, he opens b...

You’re right. I forgot that you had to tell him which door you wanted to open (instead of just saying that you've decided on a door - like the FBI as just SAID that they've cracked the iPhone5). But it doesn’t matter because Monty was always going to open one of the two goat doors, and the one that he opens doesn’t matter to the 1/3 probability that you picked the car door. Your probability of getting the car ALWAYS doubles when you switch (even though you still may not get it).
He does care. 2/3 of the time, your choice forces his. If you choose a goat, Monty doesn't have a choice. He can only reveal the other goat.

The other 1/3 of the time, you're right, he doesn't care, because he can choose any of the remaining doors at random.