Build Tool 3

Bayesian Prior Calculator

Document prior probability reasoning, convert prior probability to odds, apply a likelihood ratio, and calculate posterior probability for transparent professional review.

Safety and ethics

This calculator supports transparent Bayesian reasoning and documentation. It does not determine truthfulness, deception, guilt, innocence, suitability, or admissibility. Outputs depend entirely on the assumptions entered and must be interpreted by a qualified professional.

Legal and professional-use disclaimer

This tool is provided for qualified professional, research, educational, and documentation purposes only. It is not legal, clinical, investigative, or forensic advice and must not be used by unauthorised persons to make decisions about truthfulness, deception, guilt, innocence, suitability, risk, employment, relationship status, admissibility, or any legal right or obligation. Any unauthorised or non-professional use is at the user's own risk. Final decisions remain with appropriately qualified professionals.

1. Case Information

Case reference

Examination type

Examinee role

Date

Examiner

Allegation/issue

Notes

2. Prior Probability Builder

Initial prior probability (%)

Confidence in prior

Interpreting as certainty?

Rationale for prior

Structured prior factors

3. Prior Odds Calculator

Prior probability-

Prior odds-

Interpretation-

4. Likelihood Ratio Input

Example labels below are illustrative placeholders only, not scientific claims about any specific test.

LR for deception-supporting result

LR for truthfulness-supporting result

Result direction to apply

Manual LR used

Conservative/weak LR

Moderate LR

Strong LR

LR source/rationale

Examiner notes

5. Posterior Calculator

LR used-

Posterior odds-

Posterior probability-

Before

After

Change from prior: -

6. Scenario Comparison

Scenario	LR	Posterior probability

7. Sensitivity Analysis

Prior probability: 25%

Likelihood ratio: 3

Sensitivity posterior probability-