Which statement about interpreting DNA evidence with a likelihood ratio is accurate?

Which statement about interpreting DNA evidence with a likelihood ratio is accurate?

• A. A high LR means stronger support for the non-contributor hypothesis.
• B. LR is a simple count of matching alleles.
• C. LR is the probability that the data were observed given a random match.
• D. A high LR means the data are more supportive of the contributor hypothesis than the non-contributor hypothesis.

Answer: (D)

The likelihood ratio compares how probable the observed DNA pattern is under two competing explanations: that the known person contributed, versus that someone else contributed. It is calculated as P(data | contributor) divided by P(data | non-contributor). A large ratio means the data fit the contributor hypothesis much better than the alternative, so it strengthens support for the contributor hypothesis. This is why the statement that a high LR makes the data more supportive of the contributor hypothesis than the non-contributor hypothesis is the accurate one. It's not a simple allele-count; it's a ratio of probabilities that also reflects how common or rare the observed pattern would be in the population. Nor is it the probability of a random match by itself—the LR compares two hypotheses, not just one probability in isolation.

The likelihood ratio compares how probable the observed DNA pattern is under two competing explanations: that the known person contributed, versus that someone else contributed. It is calculated as P(data | contributor) divided by P(data | non-contributor). A large ratio means the data fit the contributor hypothesis much better than the alternative, so it strengthens support for the contributor hypothesis. This is why the statement that a high LR makes the data more supportive of the contributor hypothesis than the non-contributor hypothesis is the accurate one. It's not a simple allele-count; it's a ratio of probabilities that also reflects how common or rare the observed pattern would be in the population. Nor is it the probability of a random match by itself—the LR compares two hypotheses, not just one probability in isolation.