You judge an odds ratio of 15:85 for the money having been yours versus it having been Nick’s, which presumably decomposes into a maximum entropy prior (1:1) multiplied by whatever evidence you have for believing it’s not yours (15:85). Similarly, Nick has a 80:20 odds ratio that decomposes into the same 1:1 prior plus 80:20 evidence.
In that case, the combined estimate would be the combination of both odds ratios applied to the shared prior, yielding a 1:1 * 15:85 * 80:20 = 12:17 ratio for the money being yours versus it being Nicks. Thus, you deserve 12⁄29 of it, and Nick deserves the remaining 17⁄29.
Yeah, I made a pointlessly longer calculation and got the same answer. (And by varying the prior from 0.5 to other values, you can get any other answer.)
My take on it:
You judge an odds ratio of 15:85 for the money having been yours versus it having been Nick’s, which presumably decomposes into a maximum entropy prior (1:1) multiplied by whatever evidence you have for believing it’s not yours (15:85). Similarly, Nick has a 80:20 odds ratio that decomposes into the same 1:1 prior plus 80:20 evidence.
In that case, the combined estimate would be the combination of both odds ratios applied to the shared prior, yielding a 1:1 * 15:85 * 80:20 = 12:17 ratio for the money being yours versus it being Nicks. Thus, you deserve 12⁄29 of it, and Nick deserves the remaining 17⁄29.
Yeah, I made a pointlessly longer calculation and got the same answer. (And by varying the prior from 0.5 to other values, you can get any other answer.)