I have been asked a question about how/why RuneScape's drop mechanics work the way they do and I need help because I am horrible inept at statistics
Basically, in a lot of content across runescape, the 'drops' are rolled in two different ways, a simplified example
Single Roll:
The boss drops 2 rare items, each with a rarity of 1/x. When killed there are x options rolled for, 1 of which is each separate rare item, all the others are undesirable drops.
So you have a 2/x chance of getting a rare, and each rare has the same chance of being obtained.
Double Roll:
Now imagine the same boss, who drops the same 2 rare items, but when killed the boss rolls x/2 options, only 1 of which is for 'any rare item'. If the any rare item roll is hit, a secondary roll is produced that can only produce rare items, each unique item having a probability of 1/2 (once you have rolled for the x/2 rare drop access)
On the face of it there seems to be literally no difference in the end user perspective to me, you are still just as likely to get one or the other and can balance the droprates accordingly. Yet I figure they must surely use the two systems for a reason.
So the question I have been posed, specifically, is as follows:
Imagine you want to 'complete' the content by getting both unique drops (so not just two drops, as this could give you a duplicate item, but both unique separate drops obtained at least one time), is there any difference in the likely number of necessary drops needed to get the two uniques by using the one or two roll system? Are you more or less likely to 'go dry' using either system and if there is a difference, how is it effected by extremely extensive content with far more than 2 unique drops necessary (i.e the 'rare' roll is between dozens of items)?
In fact is there any difference in how the drop rates would work for the actual player, or could the difference in the drop tables just be some behind the scenes coding shit to make it simpler?
Basically, in a lot of content across runescape, the 'drops' are rolled in two different ways, a simplified example
Single Roll:
The boss drops 2 rare items, each with a rarity of 1/x. When killed there are x options rolled for, 1 of which is each separate rare item, all the others are undesirable drops.
So you have a 2/x chance of getting a rare, and each rare has the same chance of being obtained.
Double Roll:
Now imagine the same boss, who drops the same 2 rare items, but when killed the boss rolls x/2 options, only 1 of which is for 'any rare item'. If the any rare item roll is hit, a secondary roll is produced that can only produce rare items, each unique item having a probability of 1/2 (once you have rolled for the x/2 rare drop access)
On the face of it there seems to be literally no difference in the end user perspective to me, you are still just as likely to get one or the other and can balance the droprates accordingly. Yet I figure they must surely use the two systems for a reason.
So the question I have been posed, specifically, is as follows:
Imagine you want to 'complete' the content by getting both unique drops (so not just two drops, as this could give you a duplicate item, but both unique separate drops obtained at least one time), is there any difference in the likely number of necessary drops needed to get the two uniques by using the one or two roll system? Are you more or less likely to 'go dry' using either system and if there is a difference, how is it effected by extremely extensive content with far more than 2 unique drops necessary (i.e the 'rare' roll is between dozens of items)?
In fact is there any difference in how the drop rates would work for the actual player, or could the difference in the drop tables just be some behind the scenes coding shit to make it simpler?
