Ask our Biostatistician: Clinical Trial Sample Size Calculation

Welcome to "Ask Your Biostatistician," a new expert led series from Navitas Life Sciences. Each edition explores foundational concepts that shape clinical research success, starting with a topic that’s often underestimated but absolutely vital: sample size calculation.

Getting It Right from the Start: Strategic Sample Size Selection in Clinical Trials

In this first episode, our biostatistics experts Robert Chastain, Biostatistics SME and Dave Maslow, Clinical Data Management SME, discuss why determining sample size isn’t just a formulaic exercise but a strategic choice that impacts the power, cost, and credibility of your trial. Whether you're calculating statistical sample size for early-phase research or to plan a pivotal phase II study, getting it right from the start can make all the difference.

Authors

Robert Chastain

Biostatistics SME

Dave Maslow

Clinical Data Management SME

More Than Just a Number: The Strategic Value of Sample Size

It’s tempting to think of sample size as just a number derived from a formula or a clinical trial sample size calculator. But in reality, determining sample size is a strategic decision with far-reaching consequences.

Selecting a statistically significant sample size that’s too small can jeopardize your ability to detect meaningful treatment effects. Too large, and you're potentially burning through valuable resources. With patient costs ranging between $75,000 and $125,000, a miscalculation of just 10 patients could result in over $1 million in unnecessary spending.

The right sample size calculation provides the power you need, without excess. But “getting it right” takes more than just math, it requires an understanding of clinical endpoints, statistical models, and operational realities.

A Cross-Functional Approach: Biostatistics Meets Data Management

Effective planning starts early. At Navitas, our biostatistics and clinical data teams collaborate from day one to support robust clinical trial design.

For example, if dropout rates are expected to be high, or historical clinical data shows site-specific enrollment challenges, this insight feeds directly into our process for calculating statistical sample size. These adjustments upfront help improve the accuracy of your clinical trial sample size calculation and ensure you’re prepared for a range of outcomes.

Planning for Uncertainty: Scenario Simulations

We don’t just calculate sample size once and move on. Our team runs detailed simulations to assess what happens when trial variables shift.

What if the treatment effect is smaller than anticipated? What if data variance increases? By calculating sample size across different scenarios, we give sponsors the foresight to make informed decisions—and avoid costly amendments later.

Real-World Feasibility Matters

Designing a statistically sound trial is only half the battle. A model may suggest a significant sample size, but can it be realistically achieved?

We assess feasibility as part of our sample size calculation process. That means verifying whether enrollment targets are practical, timelines are achievable, and whether the clinical data infrastructure can support clean interim and final analyses. Our integrated approach ensures that your statistically significant sample size is also operationally viable.

Regulatory-Ready Documentation and Adaptive Strategies

We tailor every output to your trial’s unique design. From visual power curves to scenario planning reports, our documentation supports submission-ready quality and regulatory clarity.

When appropriate, we support adaptive designs—allowing for adjustments to the sample size during the trial based on interim data. These strategies align with evolving regulatory frameworks, including the January 2025 revision of ICH E6 (GCP), enabling flexible, efficient trial designs without compromising scientific rigor.

Beyond the Numbers: A Partner in Trial Success

At Navitas, our statisticians do more than just calculate sample size. We’re strategic partners in your success—balancing scientific methodology, clinical data realities, and operational constraints to recommend the most appropriate and effective sample size for your study.

Whether you're designing a first-in-human Phase 1 study, a pivotal Phase 3 trial, or post-marketing surveillance, our experts are ready to support you with biostatistics-driven planning and execution.

Let’s Talk About Your Trial

Need help calculating sample size for your next study? Curious about how a clinical trial sample size calculator fits into a broader strategy? Whether you're still planning or revisiting a current program, let’s talk. Our biostatistics and Clinical Data Management team are here to help design a trial that’s powered for success.