number generators

[budgie]

does a random generated number appear more than once

[Drewhound]

It can. Any number once generated has exactly the same chance as all the other nunbers to be generated the next time EG if you toss a coin and it lands heads up the chance is still 50/50 the next throw

[New Forester]

But it's very hard indeed to design a truly random number generator. Most just get very close, but because they are using a set of rules to generate the numbers, they are open to slight bias. This applies whether it's done mathematically or physically, as with lottery balls -- for example the balls will vary very slightly in weight and shape. In practice, tossing a coin and many other popular methods are as random as you need for most things. As a student I remember we had mathematically generated "random" number tables, and you took them in order to decide which little seedling got which treatment or whatever. Some natural numbers appear to be random -- such as the digits of the constant pi. But maybe they are not...

[Potatoman]

pi is not a random number, it is a constant

[Maxrom]

You don't mention how the random numbers you refer to are being generated, but if they're generated using a computer, then the answer is a definate yes. Depending on the logic used, it may take millions, billions or more iterations before it's repeated, but it will be repeated at some point. This is because it's not possible for any conventional computer to generate a truly random number. A number sequence from a PC may appear to be random, but it is actually based upon a seed number, and calulated from that. If you provide the same seed number, the same set of seemingly random numbers will be generated every time. There are ways to make this less obvious (using a seed number based on the date and time for example) but they're still not random. This is why the national lottery use what would appear to be a rather simplistic approach to picking numbers. By having balls bouncing around in a container, you can generate a truly random result (although ball weight, and other factors could be used to argue this isnt' truly random either, but it's as close as you're going to get). If the national lottery used a computer instead, once the seed number, and seudo-random number generator algorithm were disclosed, everyone could get the winning numbers, every time, because the numbers wouldn't be random, but would follow a set pattern. This is also why, when buying a lottery ticket, I never use the 'lucky dip' option, as these numbers are picked by a computer, which is incapable of producing truly random numbers that you get from the bouncing balls on the lottery draw night. You could theoretically build a computer using some kind of fuzzy-logic to achieve this aim, but thats a whole different topic.

[budgie]

Yes, I was referring to a computer generated number. Yes your theory backs up what I thought. As for seed numbers, yes they do seem to appear more and more often. Thank you