Why Sample Size Matters in Clinical Trials

When brands boast “clinically proven” on their labels, what’s behind that claim? It’s not just clever marketing, it’s science. And at the heart of that science is sample size. Often overlooked but absolutely essential, sample size is the foundation of trustworthy clinical trials. Whether you're launching a glowing new serum, a gut-health gummy, or a calming pet chew, the number of people (or pets) in your trial can make or break how compelling your results are.

In this post, we unpack why sample size isn't just a number, it's a strategy for brand integrity, smarter marketing, and real-world results.

What Is Sample Size?

Sample size refers to the number of participants involved in a clinical trial. In the world of consumer product testing, it tells us how many people (or animals) were studied to determine whether a product works as intended.

A properly calculated sample size helps ensure that results are not due to random chance and can be confidently generalized to a broader audience. It also influences how your trial is perceived by regulators, retailers, and, most importantly, your customers.

Why Sample Size Matters

1. Boosts Credibility and Trust

A larger, well-powered sample size increases confidence in your trial’s results. It makes your data more convincing to both scientific reviewers and everyday consumers. When buyers see that a product was tested on 100 people instead of 10, they instinctively trust it more.

2. Enables Meaningful Marketing Claims

Marketing language like “clinically shown to reduce redness” or “improved skin hydration in 8 weeks” needs solid backing. The FTC requires that such claims be truthful and supported by reliable evidence. A strong sample size strengthens your case.

3. Minimizes Statistical Error

Small sample sizes can lead to misleading results. A trial with too few participants may either exaggerate the benefits or completely miss them. By optimizing sample size, you reduce the risk of these statistical pitfalls.

The Balancing Act: Cost vs. Confidence

Conducting a clinical trial involves time and investment. Naturally, larger sample sizes mean higher costs. But underpowered studies can be even more expensive in the long run, especially if inconclusive results force a redo.

Thanks to decentralized clinical trials and digital recruitment tools, brands today can strike a smarter balance. You can maintain scientific integrity without draining your budget by planning ahead and selecting the right trial partner.

How to Determine the Right Sample Size

Several factors go into calculating the ideal sample size for your trial:

• Effect size: How big of a difference do you expect your product to make?

• Population variability: How much variation exists in participant responses?

• Confidence level: How certain do you want to be in the results (typically 95%)?

• Statistical power: How likely are you to detect an actual effect (commonly 80%)?

This calculation should be performed by a statistician or a clinical trial expert to ensure your study is robust and credible.

What Counts as a "Good" Sample Size?

There’s no one-size-fits-all answer, but here are some industry norms:

• Pilot studies or early-stage trials: 30–50 participants

• Mid-scale validation trials: 75–100 participants

• Large-scale confirmatory studies: 100+ participants

For claims intended to appear on product packaging or in national marketing campaigns, the higher end of this range is usually more appropriate.

When Small Sample Sizes Still Work

Not every trial needs to enroll hundreds of people. For niche products or exploratory trials, smaller sample sizes can still yield useful insights, as long as limitations are transparently reported. These studies can serve as a stepping stone for larger, more definitive trials later on.

Make Every Participant Count

In clinical trials for consumer products, sample size is more than just a number, it’s a message. It tells your customers, your partners, and your critics that you’ve done the work. That your claims are backed by data. And that your product doesn’t just promise results, it delivers them.

Whether you're developing the next great wellness supplement or an innovative pet product, investing in the right sample size means investing in long-term success.

Looking to lock down your ideal sample size for your research study? Try CitrusMatch for free and find your perfect study design in under two minutes.