Two Generation Bayes Update
Apply sequential family-evidence likelihood ratios from two generations to a prior risk.
Description
Bayesian updating converts prior probability and evidence likelihood ratios into posterior probability.
Bayesian updating converts prior probability and evidence likelihood ratios into posterior probability. Sequential ratios can summarize conditional evidence from successive generations.
Apply sequential family-evidence likelihood ratios from two generations to a prior risk.
When to use Two Generation Bayes Update
Use this for the following task: Apply sequential family-evidence likelihood ratios from two generations to a prior risk.
Prepare the observed records or explicit model parameters requested below. Keep probabilities as fractions and paired records aligned.
How to use Two Generation Bayes Update and understand its results
- Prepare the observed records or explicit model parameters requested below. Keep probabilities as fractions and paired records aligned.
- Enter priorRisk, firstGenerationLikelihoodRatio, secondGenerationLikelihoodRatio using the field table, then run the tool.
- Read afterFirstGeneration, afterSecondGeneration. Interpret flags, units, ordering and placeholder values using the rules below.
- Review any reported issue or failed check, correct the supplied values when appropriate, and verify the result in its intended context.
| Input field | Meaning | Value type and bounds | Requirement |
|---|---|---|---|
| priorRisk | Prior risk | number | Required |
| firstGenerationLikelihoodRatio | First generation likelihood ratio | number | Required |
| secondGenerationLikelihoodRatio | Second generation likelihood ratio | number | Required |
Require prior risk in [0,1] and positive likelihood ratios. Apply the first update, then use that posterior as the prior for the second.1
update(p,LR) = p LR/(1−p+p LR) This summarizes the declared operation. Units, indexing, inclusivity and exceptional cases are explained in the surrounding text.
| Output field | Meaning | Value type |
|---|---|---|
| afterFirstGeneration | After first generation | number |
| afterSecondGeneration | After second generation | number |
{
"input": {
"priorRisk": 0.1,
"firstGenerationLikelihoodRatio": 2,
"secondGenerationLikelihoodRatio": 3
},
"output": {
"afterFirstGeneration": 0.18181818181818182,
"afterSecondGeneration": 0.4
}
}Limitations and assumptions
Likelihood ratios must be appropriately conditioned to avoid double-counting related evidence. The tool does not estimate them from a pedigree.
The tool evaluates supplied observations or a declared model. It does not establish the biological cause of an observed pattern. Malformed requests produce input errors. A successfully evaluated request can still contain false flags, empty result lists or a result outside the supplied threshold; those outcomes have the meanings stated above.
Alternative or Complementary methods
Choose Negative Screen Residual Risk for this operation: Update carrier risk after a negative screen using explicit prior risk, sensitivity, and specificity. For a complementary task, use X Recessive Son Risk for this operation: Compute an X-recessive carrier-mother son-risk model with explicit carrier prior, birth sex probability, and penetrance.
The implementation reference documents the exact calculation, supported input shapes and returned fields.
References
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Two Generation Bayes Update — tool.io
Similar or alternative tools
- Negative Screen Residual Risk
Update carrier risk after a negative screen using explicit prior risk, sensitivity, and specificity.
- X Recessive Son Risk
Compute an X-recessive carrier-mother son-risk model with explicit carrier prior, birth sex probability, and penetrance.