Problem ID: C12-126 Model: GPT 6 Astra Ultra Version: 1
Pre-analysis commitments compatible with adaptive experimentation
Status. Unresolved for optimal discovery across general adaptive targets. The results below give a checkable commitment rule and a treatment-budget separation bound in one restricted experiment.
Short problem and statistical model
A pre-analysis commitment fixes a measurable program before observations arrive. The program may adapt allocations and create hypotheses; the aim is familywise error at most $\alpha$ at every time and useful discovery power under an expected treatment budget. Let $\mathcal F_t$ contain observations and authorized randomness through time $t$. A launched test $j$ has stopping-time launch $\sigma_j$, an $\mathcal F_{\sigma_j}$-measurable level $a_j\geq0$, and subsequently observed scores $X_{jt}\in[-1,1]$. Its null is the
conditional assertion \[
H_j:\quad {\mathbb{E}}[X_{jt}\mid\mathcal F_{t-1}]\leq0\quad(t>\sigma_j).
\] A newly chosen target must meet this assertion under its claimed null after conditioning on the history that chose it. Unconditional zero means are insufficient. Assume countably many launches and $\sum_j a_j\leq\alpha$ almost surely. A test with $a_j=0$ never rejects. For each fixed sampling law, whether a launched hypothesis is true is required to be measurable at its launch; its conditional score restriction must hold on all such true-null launch histories.
Theorem (Commitments that survive predictable updates): For $t>\sigma_j$ choose $\mathcal F_{t-1}$-measurable bets $\lambda_{jt}\in[0,1]$, and define \[
E_{jt}=\prod_{s=\sigma_j+1}^{t}(1+\lambda_{js}X_{js}).
\] Reject $H_j$ only if $E_{jt}\geq1/a_j$. Under every law for which the declared true nulls obey their conditional score restrictions, the probability of ever rejecting any true null is at most $\alpha$. The assertion permits adaptive assignment, adaptive bets, and history-selected hypotheses launched on future observations.
Proof: Under a true null the factors are nonnegative and their conditional means are at most one, so $E_{jt}$ is a nonnegative supermartingale starting at one at its launch. For any finite horizon, stop at its first crossing of $1/a_j$ or the horizon. Conditional expectation at the launch is at most one; on crossing the stopped value is at least $1/a_j$. Thus the conditional crossing probability is at most $a_j$. Increasing the horizon gives the same bound for ever crossing. Multiply by the history-measurable indicator that the selected null is true, take expectations and sum over launches. The union bound gives at most ${\mathbb{E}}\sum_j a_j\leq\alpha$. If truth is represented by a law-dependent conditional hypothesis, the same proof applies on launch histories where the conditional restriction holds. ∎
For example, at time $t$ let potential outcomes lie in $[0,1]$, randomize $W_t$ with predictable known $p_t\in[\epsilon,1-\epsilon]$, independently of that unit's potential outcomes conditional on past information. Set \[
X_t=\epsilon\left\{\frac{W_tY_t}{p_t}
-\frac{(1-W_t)Y_t}{1-p_t}-\theta_0\right\}/2,
\qquad \theta_0\in[-1,1].
\] Then $|X_t|\leq1$, and its conditional mean is nonpositive if the next unit's conditional treatment effect is at most $\theta_0$. Changing eligibility or outcomes is valid only if the updated score still has this property. A null about a population average alone need not imply it for outcome-adaptively selected subpopulations.
An information limit imposed by the budget
Consider a fixed horizon $T$. Control responses are Bernoulli$(1/2)$ under both laws. Treatment responses are independent Bernoulli$(1/2)$ under $P_0$ and Bernoulli$(1/2+\Delta)$ under $P_\Delta$, where $0<\Delta\leq1/4$. Conditional assignment kernels may adapt to all previous observations, but the same committed kernel is used under both laws. Write $N_T=\sum_{t\leq T}W_t$. We impose ${\mathbb{E}}_0N_T\leq bT$, where $0<b<1$.
Proposition (Budget lower bound for any adaptive test): For any rejection event $R\in\mathcal F_T$ with $P_0(R)\leq\alpha$, \[
P_\Delta(R)\leq\alpha+\sqrt{\frac43 bT\Delta^2}.
\] Thus power bounded away from size requires $bT\Delta^2$ bounded away from zero, even when assignments and stopping decisions adapt.
Proof: Factor the joint likelihood sequentially. The assignment factors cancel, as do control-response factors. Taking expectation under $P_0$ gives \[
{\operatorname{KL}}(P_0,P_\Delta)={\mathbb{E}}_0N_T\,
{\operatorname{KL}}(\mathrm{Ber}(1/2),\mathrm{Ber}(1/2+\Delta))
={\mathbb{E}}_0N_T[-\tfrac12\log(1-4\Delta^2)].
\] For $4\Delta^2\leq1/4$, the last bracket is at most $2\Delta^2/(1-4\Delta^2)\leq(8/3)\Delta^2$. Pinsker's inequality and $P_\Delta(R)\leq P_0(R)+{\operatorname{TV}}(P_0,P_\Delta)$ prove the claim. The calculation includes internal randomization by adjoining its common law to the experiment. ∎
Proposition (A budget-feasible anytime test with power): Use independent assignments $W_t\sim\mathrm{Ber}(b)$ and the prespecified alternative $\Delta\in(0,1/4]$. For the null that treatment success probability is at most $1/2$, define \[
L_t=\prod_{s\leq t}\{1+2\Delta(2Y_s-1)\}^{W_s}.
\] Reject when $L_t\geq1/\alpha$. The test is valid at every time, satisfies ${\mathbb{E}} N_T=bT$, and, if $bT\Delta^2\geq3\log(1/\alpha)$, has power by $T$ at least \[
1-\exp(-bT/8)-\exp(-bT\Delta^2/16)
\] under $P_\Delta$.
Proof: Each factor has conditional expectation at most one under the null, giving the preceding supermartingale argument. Under the alternative, $N_T$ is binomial and ${\mathbb{P}}(N_T<bT/2)\leq e^{-bT/8}$. Conditional on assignments, the $N_T$ treated responses are independent with mean $1/2+\Delta$. Their empirical mean is at least $1/2+3\Delta/4$, except with probability $e^{-N_T\Delta^2/8}$ by Hoeffding. The mean log likelihood for a treated response is ${\operatorname{KL}}(\mathrm{Ber}(1/2+\Delta),\mathrm{Ber}(1/2))\geq2\Delta^2$ by Pinsker. Also \[
\log\frac{1+2\Delta}{1-2\Delta}
=\int_0^{2\Delta}\frac{2\,du}{1-u^2}\leq\frac{16}{3}\Delta.
\] Reducing the empirical success frequency from its mean by $\Delta/4$ therefore leaves average log likelihood at least $(2/3)\Delta^2$. On the two good events, $\log L_T\geq bT\Delta^2/3\geq\log(1/\alpha)$. Their failure probabilities give the bound, and crossing by $T$ follows from $L_T$ crossing at $T$ if it has not crossed earlier. ∎
Remaining gap
The lower and upper results isolate the effective information budget $bT$, with logarithmic confidence costs in the constructive test. They do not optimize allocation across multiple unknown alternatives, outcome definitions or eligible populations. The test uses a prespecified effect size; mixtures of such likelihood processes remain valid, but their optimal discovery utility and selection costs are not characterized here. Registration alone does not verify a conditional score inequality, and the theorem supplies no causal justification for an outcome or population selected after observing its responses.
Reference and provenance
Carlos Cinelli, Avi Feller, Guido Imbens, Edward Kennedy, Sara Magliacane and Jose Zubizarreta (2025),
Challenges in Statistics: A Dozen Challenges in Causality and Causal Inference, arXiv:2508.17099v1, Section 3.1.3, "Automation and reducing frictions."
https://arxiv.org/html/2508.17099v1. This is the inspected source of the agenda. The supermartingale construction is a standard method, proved here; the restricted budget calculation does not claim an optimal general adaptive discovery program.
Completion Estimate
35%