Event
Definition
Any subset of the sample space to which a probability is assigned. An event may be a single outcome (this particular allele) or a collection of outcomes (any allele with frequency above 0.05). Forensic probability statements are always about events, not individual measurements.
- Field
- Probability theory, forensic statistics
- Definition scope
- Any subset of the sample space with an assigned probability
- Can be
- A single outcome or a collection of outcomes
- Forensic application
- Statements are about events, not individual measurements
Common questions
Why does forensic probability language use the term event rather than measurement?+
A raw measurement, like an allele frequency, is a data point, while an event is the specific proposition being assigned a probability, such as observing that allele or a broader category of alleles, which keeps the statistical claim precisely defined for a court.
Can an event in this sense combine multiple individual outcomes?+
Yes, an event can be defined broadly, such as any allele with a frequency above a stated threshold, grouping several individual outcomes under one probability statement rather than requiring a separate calculation for each specific outcome.
Why does defining the event precisely matter for likelihood ratio calculations?+
A likelihood ratio compares the probability of the same defined event under two competing hypotheses, so if the event is vaguely or inconsistently defined, the resulting ratio does not represent a coherent comparison and can mislead the fact-finder.
Related terms
- Complement
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- Conditional Probability
- The probability of event A given that event B has already occurred, written P(A|B). Conditional probability is the basis of the multiplication...
- 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...
- 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...
- Sample Space
- The set of all possible outcomes of an experiment. In forensic genetics, the sample space for a single allele call is the...