Forensic parameters - An Introduction to Forensic Genetics - page 181

Appendix A Forensic parameters

Match probability

The probability that the two randomly selected individuals within a population will
have identical genotypes at a locus.

Formula:

m

p k p M =

k = 1

where p M is the match probability of individual locus, p k represents the frequency
of each distinct genotype that is possible (which in turn depends on the number of
alleles at the locus), m is the number of the distinctive genotypes.

Power of discrimination

The probability that two randomly selected individuals will have different genotypes.

Formulae:

For a single locus the formula is: p D = 1 − p M

n

For several loci the formula is: P Dcomb = 1 −

1 (

1 − P Di )

i =

where, p D is the power of discrimination of a single locus, p M is the match probability
of a single locus, P Dcomb is the power of discrimination of several loci, P Di is the
individual locus power of discrimination and stands for multiplication.

Power of exclusion

Is the fraction of the individuals that is different from that of a randomly selected
individual. It can also be defined as the power of a locus to exclude a person being