Premium Bond Query??

Malthusian

lowbrim wrote: »

Just to clarify I do not have a 20k batch my biggest batch is 5000. of which I have a few and I still find it unusual that whenever I get more than one win they are invariably out of the same batch.

Could you make your mind up over whether it is "invariably" (i.e. every single time, without variation) or "less than one third of the time"?

We can't really have a sensible discussion about statistics if the opening statement is "This coin is loaded, it comes up tails every single time, apart from the 50% of times it doesn't."

coyrls

Put it this way: having a winning bond picked from a batch doesn't reduce the chance of another winning bond being picked from the same batch.

IanSt

lowbrim wrote: »

Just to clarify I do not have a 20k batch my biggest batch is 5000. of which I have a few and I still find it unusual that whenever I get more than one win they are invariably out of the same batch.

How many of these big batches do you have?

If you had just the one, then yes it would be unusual for such an occurrence to continue, but not mathematically impossible and random numbers can look to be very unusual. However if you've got 10, then it's a lot less unusual.

With ten batches that can happen a lot more than you may think. For instance it only needs 23 random people to be in a room for there to be a 50% chance that two of them have the same birthday.

Zanderman

lowbrim wrote: »

Can anyone explain to me why when I win more than one premium bond prize in a month that invariably (around 30% of the time) the winning premium bonds are out of the same batch. I would have thought that if each bond had equal chance of winning that the chances of getting two bond winning in the same month out of the same batch would be almost impossible but it happens on very regular basis. Am I missing something ??

Perhaps think about this hypothetical scenario:

You have 20 bonds.

10 are individuals, not in a sequence.

The other 10 are a sequence of 10.

Each of those 20 has an equal chance of winning, as winning is random.

But, on average, 50% of the wins will be from one of those in the sequence.

So you will think the 'sequence' ones win more often than the individuals, as 50% of wins are from the sequence.

But it's an illusion. Every bond has an equal chance. You just associate the sequenced ones as somehow linked. They aren't.

If your sequence is a long sequence the illusion is greater.