That is indeed another problem I did not consider. It definitely decreases the value of knowing how many people others have a crush on in general. But still, the fact how many people have a crush on me in particular should be somewhat correlated to how many people they have a crush on in general. Since, as you pointed out, it is impossible for me to get the specific percentage for myself I’ll have to go with the general one.
Concerning your juggling comparison. Maybe I did not express myself clearly. If you want to find out if someone likes you, then of course the most important thing is interacting with him/her. It is way more important than knowing the prior. I do not expect that after finding out the prior and reading about flirting signals I will be able to skip Interacting with people. I believe it will help me interpreting the interaction with people the right way.
The only way I can see the prior being irrelevant is when flirting signals are 100% perfect filters. Let us say I am flirting with someone and giving a signal and getting a response. If that person gives that response 100% to a person she has a crush on and 0% to a person she does not have a crush on than the prior would indeed be irrelevant. If however this person gives the response with 100% Chance to a Person he/she has a crush on, but also with 50% chance to a person he/she just likes as a friend, then this signal will only help me differentiate between the states "friend" and "love intrest" with 50% probability. And now it becomes relevant on how many of his/her friends this person has a crush.
Let us say the person has 10 friends and has a crush on 5 of them. Than on average he/she would give 5 correct positive signals 2.5 false positive signals and 2.5 correct negative signals. So if I get a positive signal, than that means that with a probability of 2/3 that person would have a crush on me and with a probability of 1/3 he/she would not.
If that same person would only have a crush on one of his/her 10 friends than on average he/she would give 1 correct positive signal 4,5 false positive signals and 4,5 correct negative signals. So if I would get a positive signal in this case than with a probability of 18% (1/4.5+1)) that person would have a crush on me and with probability of 82% (4.5/4.5+1)) he or she would not have a crush on me.
So in the first case I am reasonably sure that the other person has a crush on me and can proceed giving more obvious hints, while in the second case I should still gather more information before moving on to the next stage.
I am of course aware that in real live I will not know the exact probability for how often a certain signal is given to a friend or a love interest, but I can still get acceptable estimates for that.
Is there anything wrong with this reasoning or do you just thing that flirting signals are usually 100% perfect filters?
Flirting signals aren't just positive and negative.
If a girl is nervous when around you when she isn't nervous while around other people and there no real reason to be nervous, that can be a sign that she has a crush.
At the same time it can also be a sign that a girl likes you when she's very relaxed while around you, has open body language and is comfortable with physical touch. Crucially more comfortable being touched by you than being touched by other people.
If you have a crush on someone you usually want to find out if they have one on you too. In my opinion outright asking them is often not a good solution, because if they don't have a crush on you yet it decreases the chance of this ever happening if they know you have one. This believe is based on what I read about love psychology. Hovever I don't really want to discuss the option of outright asking them in this thread, therefore I have not elaborated further how I got to this believe.
The alternative to asking them is trying to interpret signals that they might give you. However to know how many signals you need before you should believe that they are in love with you, you would need the prior. I have not been able to find anything about the prior of someone being in love with you. Therefore my Idea is to do a survey in order to find out how likely it is that a person you know has a crush on you. The plan is to ask the person taking the survey how many people they know well enough to possibly have a crush on them and how many people they actually have a crush on.
I have created a Survey for this and would be really happy if you would participate.
The next stepp would be to discuss how certain signals a person can give you raise the probability of them having a crush on you. That part is quite difficult. I think probably the best way would be to check how your friends react to certain situations and what body language they show you and then, if you find out someone has a crush on you, to look up what he did differently from people who are merely your friends. I am currently not in a good position to do this experiment but if someone wants to try or has results about this to share please do so. However I think this part is less important than finding the prior, because most people have at least a general idea about what certain signals mean from personal experience while at least I have no idea at all what the prior might be.