Conditional probability
Definition
The probability of event A given that event B has already occurred, written P(A|B). Conditional probability is the basis of the multiplication rule in its general form and the foundation of the likelihood ratio framework used in evaluative forensic reporting. It is treated in depth in the next topic.
Related terms
- Complement
- A group of heat-labile serum proteins (approximately 30 proteins, designated C1 through C9 in the classical pathway) that can be activated by...
- Event
- Any subset of the sample space to which a probability is assigned. An event may be a single outcome (this particular allele)...
- Hardy-Weinberg equilibrium
- A condition in a population where genotype frequencies at a single locus conform to expectations derived from allele frequencies alone, assuming random...
- Independent events
- Two events where the occurrence of one provides no information about the other: P(A and B) = P(A) x P(B). In forensic...
- Linkage disequilibrium
- The non-random association of alleles at different loci within a population. Certain HLA allele combinations (e.g., HLA-A1 with HLA-B8 with HLA-DR3) occur...
- Multiplication rule
- For any two events: P(A and B) = P(A) x P(B|A). When A and B are independent, this simplifies to P(A) x...
- Mutually exclusive events
- Two events that cannot both occur in the same trial. If a fibre is classified as cotton, it cannot simultaneously be classified...
- Positive dependence
- Events are positively dependent when the occurrence of one increases the probability of the other: P(A|B) > P(A). In this case P(A...
- Sample space
- The set of all possible outcomes of an experiment. In forensic genetics, the sample space for a single allele call is the...
- Statistical independence
- Events A and B are independent if P(A|B) = P(A), equivalently P(A and B) = P(A) x P(B). Knowing B occurred gives...
Explained in these topics
- Basic Probability RulesThe probability of event A given that event B has already occurred, written P(A|B). Conditional probability is the basis of the multiplication rule in its gene...
- Conditional Probability and IndependenceThe probability of event A given that event B has occurred, written P(A|B) = P(A and B) / P(B). It updates the probability of A in light of new information abo...