What a match found by trawling a database is worth. np is the bound of
the second National Research Council report: the match probability times
the number of profiles searched. any is the exact chance of at least one
chance match among that many unrelated profiles, never above np. post
takes the other view (Balding and Donnelly): everyone else in the database
was excluded, so among pop possible sources with equal prior the matching
person's probability of being the source goes up, not down. See
proof("dbsrch").
Usage
dbsrch(mp, n, pop = NULL)
Arguments
- mp
The profile match probability: one number above 0 and at most 1.
- n
The number of profiles searched, the match included.
- pop
NULL, or the number of possible sources, at least n.
Value
A named numeric vector: np, any and, when pop is given,
post.
References
Balding, D. J. and Donnelly, P. (1996). Evaluating DNA profile
evidence when the suspect is identified through a database search.
Journal of Forensic Sciences, 41(4), 603-607.
Examples
dbsrch(mp = 1e-9, n = 5e6, pop = 3e7)
#> np any post
#> 0.005000000 0.004987521 0.975609756
