FA-63398 / Actuarial life tables / Member archive

Fractional age survival assumptions: Constant-force survival is linear · case 03

Constant-force survival equals the UDD value.

Member previewVariant 3 · 3 implementations · 12 checks per implementation

Case contract

Input q (per 100000), t as [num, den] in [0,1], assumption udd|cfm|balducci. UDD: tp=1-tq, mu=q/(1-tq); constant force: tp=p^t, mu=-ln p; Balducci: tp=p/(1-(1-t)q), mu=q/(1-(1-t)q). Out-of-range -> 'invalid'; infinite force -> 'infinite force'; other -> 'unknown assumption'. Return [tp, mu] rounded to 8 places.

Why this case matters

Life-table arithmetic compounds across ages, so one misplaced index or assumption shifts every downstream value.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
cfm mid-year	`[0.95603, 0.0920495]`	`[0.95501832, 0.0920495]`	Failed

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