Clinical Study Design and Feasibility
Get an endpoint hierarchy, transparent two-arm sample-size estimates, and a recruitment-based study feasibility decision.
Before & after
Same prompt, same agent — the only difference is the skill.
That's an interesting clinical research question. Designing a prospective study requires careful planning around endpoints, sample size, and study design. I could help you think through some of the key decisions you'd need to make: what specific health outcome you're measuring, whether you're comparing against a control group, how long the study would run, and how many participants you'd need. There are also regulatory and statistical considerations that matter a lot. To give you real guidance, I'd want to know more about your hypothesis, your patient population, and what resources you have available. Have you worked with a biostatistician before? That's usually helpful for study design.
CLINICAL RESEARCH STUDY DESIGN — Weekly Calls for Type 2 Diabetes: STUDY CLASSIFICATION: Type: Two-arm prospective RCT (randomized controlled trial) Phase: Phase 2 effectiveness (proof of concept, not pivotal) Primary endpoint: HbA1c reduction at 12 weeks (surrogate endpoint flagged — monitors glycemic control but not hard outcomes like MI/death) PRIMARY ENDPOINT DEFINITION: • Measure: HbA1c drop from baseline • Target: 1.2 percent reduction (clinically meaningful = 0.5 percent) • Timeline: Baseline, 6 weeks, 12 weeks • Success gate: Non-inferiority vs. standard care (not superiority — conservative estimate for weekly calls) SECONDARY ENDPOINTS: • Patient engagement: Call adherence (target 80 percent) • Medication adherence: Pill counts (exploratory) • Quality of life: DQOL questionnaire score (key-secondary, not exploratory) • Adverse events: Hypoglycemia episodes (exploratory) SAMPLE SIZE ESTIMATION (TWO-ARM DESIGN): • Baseline HbA1c: 8.2 percent (typical T2D at presentation) • Expected improvement: 1.2 percent for intervention, 0.4 percent for control • Power: 80 percent (detect true difference if it exists) • Alpha (false positive rate): 0.05 • Attrition: 15 percent • CALCULATED N: 92 participants total (46 per arm) STUDY SCHEDULE: • Enrollment window: 8 weeks • Active intervention: 12 weeks • Follow-up: 4 weeks post-study • Total duration: 24 weeks (6 months) GO / GO-WITH-CONDITIONS / NO-GO PHASE GATE: → DECISION OWNERS: Principal investigator (MD), biostatistician (sample size math), regulatory affairs (IRB compliance) → GREEN FLAG: Sample size powered, control arm defined, HbA1c lab capacity confirmed → GO (proceed to enrollment) → YELLOW FLAG: Attrition modeling shows 25% dropout risk; budget for 130 enrollees → GO-WITH-CONDITIONS (pilot adherence intervention first) → RED FLAG: HbA1c lab turnaround > 2 weeks; endpoint measurement delays → REDESIGN (centralize labs) DISCLAIMER: This estimate is preliminary. Consult biostatistician + regulatory team before submission. Never a clinical recommendation.
About this skill
“How many participants do we need?” is hard to answer when the endpoint, meaningful effect, and recruitment assumptions keep changing. This skill turns a prospective clinical study idea into an endpoint hierarchy, an auditable sample-size estimate, and a feasibility decision tied to actual recruitment capacity.
What it does
- Defines primary, key-secondary, and exploratory endpoints with measurement methods and assessment times.
- Flags surrogate endpoints and separates biological plausibility from evidence supporting their intended use.
- Estimates sample size for two independent arms comparing continuous outcomes, proportions, or time-to-event outcomes.
- Shows formulas, input provenance, attrition adjustments, and sensitivity to uncertain assumptions.
- Checks recruitment, follow-up, event yield, and analysis complexity against the proposed timeline.
- Recommends GO, GO-WITH-CONDITIONS, REDESIGN, or NO-GO with explicit blockers and human validation owners.
What you get
A scoped study-design brief or a focused calculation, depending on your request. Each includes stated assumptions, limits, and the clinician, biostatistician, or regulatory role responsible for validating the estimate before submission.
Best for
Clinical investigators, study teams, and research program leads developing a prospective two-arm study before protocol finalization or submission.
SKILL.md preview
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name: clinical-study-design-and-feasibility
description: >-
Develop prospective clinical study plans using explicit endpoint definitions, auditable two-arm sample-size calculations, sensitivity analysis, and recruitment feasibility gates. Use when the user says "help design our clinical study", "which endpoint should be primary", "how many patients do we need", "check our power calculation", "our recruitment target looks impossible", "is this biomarker a valid surrogate", or "should this study go ahead".
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# Clinical Study Design and Feasibility
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