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How do you identify and validate the fundamental assumptions behind a growth-driven design strategy?

✓ Verified Last reviewed by Lean Labs Next review due Dec 14, 2026

Every claim is sourced below

Start with the beliefs that would change the site if they turned out to be wrong. Those are beliefs about who the buyer is, which offer they want, what information they need before they act, and what they'll do next. Write each one as a statement that evidence could contradict. Beside it, record the evidence you already hold, then choose research that could prove the statement wrong.

Each kind of research establishes something different. An interview gives you the reasons a buyer reports for a decision. Watching someone attempt a task shows what they do on the site. A controlled comparison between two versions of a page estimates what a change did, under the conditions of that test.

Which beliefs count as fundamental

The method's description of the strategy stage connects three things to an implementation plan: what the audience needs, what the business wants the site to achieve, and a wishlist of ideas. Each connection depends on a belief. The plan says to rebuild the pricing page first because someone believes buyers leave there. The homepage leads with a certain problem because someone believes that problem is why buyers start looking.

A useful test is to ask what you'd build differently if the belief were false, and what it would cost to have built the wrong thing. A belief that decides which pages exist, which offer leads or what the homepage says first carries a large consequence. Rank by that consequence and not by the size of the edit, because a small change on the page where buyers decide can matter more than a large one elsewhere.

You find these beliefs by reading the plan one item at a time and asking what has to be true for that item to be the right work. Several items can rest on the same belief. That raises its consequence, because more of the build depends on it.

Writing an assumption so evidence can challenge it

"Our buyers care about integrations" is hard to test, because so many different results are consistent with it. Compare a version that names a person, a situation and a consequence: "Operations managers comparing us with a competitor want to confirm we connect to their accounting system before they'll book a demo." Ask operations managers about that belief, and use a page test to evaluate the change it leads to.

A belief backed by a dozen sales calls and a belief that started as one person's opinion look identical in a strategy document. Writing the source beside each one shows which beliefs need research first.

Customers, sales and support can each challenge these beliefs. Lean Labs' article on the three stages recommends talking with all three groups during strategy. In its account, customers can explain why they chose to buy, and sales reps hear the objections and questions prospects raise before signing. Support staff learn where new customers get confused.

The views overlap, and that helps. A belief about what stops a purchase can be put to sales and to customers, and the two answers compared. The same article gives a check to run before design starts. Show the draft messaging to those three groups and see whether they recognize the questions as the ones prospects ask. We go further into that research in how Jobs to Be Done and user research shape a strategy.

Research What it can tell you What it leaves open
Interviews with buyers, sales and support The reasons buyers give for a decision, and what sales and support hear from them How many buyers share that reason, and what they do on the page
Watching people attempt a task Where they hesitate, what they look for and whether they finish Why, beyond what they tell you when asked
Heatmaps, recordings and analytics What visitors did and where they left What they intended
A controlled comparison of two page versions Which version produced more of a counted action during the test Why it won, and whether the result holds on other pages or for other audiences

Matching the research to the question

The method's page on UX research starts from a question about a difficulty you've seen users have. You then pick a kind of research and interpret what it finds. The page lists interviews, surveys and task-based testing, then heatmaps and session recordings, then analytics such as events and funnels.

The choice follows from what the assumption claims. A belief about motive is best put to people who can describe their own decisions. A belief about behavior calls for watching someone do the task, or for a record of what visitors did. A click on a heatmap shows where someone clicked, and leaves open what they hoped to find there.

Before you choose the variations for a comparison, we'd investigate the cause, because a comparison can only choose among the versions you built. Jen Cardello's article for Nielsen Norman Group illustrates this with a loan application. A team that assumes people quit because the form has too many screens will test shorter forms. If the actual problem is that applicants can't find the interest rate, every variation misses it, and the test reports only which miss did best. Looking into the cause first gives the variations a better chance of addressing the actual problem.

Testing tools handle the mechanics of the comparison. HubSpot's page test, available on Content Hub Professional and Enterprise, serves two versions at the same URL and sends half of the visitors to each. The tool splits the traffic and counts the results. Choosing a variation that addresses the reason people were leaving is the team's job.

One assumption, from observation to proposed change

Suppose a company sells payroll software to restaurant groups. Its analytics show that most visitors who reach the pricing page leave without requesting a quote. That is the observation, and it's the only part the team knows.

The team's explanation is that buyers leave because the page shows no price. Written so it can be challenged, it reads: "Restaurant operators comparing payroll vendors leave our pricing page because they can't see a starting price." The proposed change is to publish one.

Before building anything, the team looks for evidence that could contradict the explanation. Suppose they interview recent customers and a few prospects who chose a competitor. They also watch several people try to work out from the page what the product would cost them. Suppose the interviews keep returning to a different worry, which is whether setup and tip reporting are included or billed separately. In the task sessions, people scroll past the plan names and say they are looking for what is included.

The observation hasn't changed, but the explanation has. The proposed change is now a section stating what each plan includes, and the starting price moves down the list.

Suppose the page has enough traffic for the team to compare the new version with the current one, and the new version brings more quote requests during the test. That supports the change on this page, for these visitors. It doesn't establish that setup is every buyer's main concern, and the team records the result with that limit. We cover how to frame and run the comparison in how to turn user insights into hypotheses and experiments.

What counts as validated

No set number of interviews or visitors settles an assumption. What you can state is what the evidence behind it is able to establish.

A controlled comparison estimates the effect of one change on one counted action, and it says little about motive. Interviews and observed tasks show what people reported and what they did. That suits a belief about reasons, or about where a task breaks down. It doesn't estimate how a change will perform across all of a page's visitors.

So record each belief with the kind of evidence it has, and check that the evidence fits what the belief claims. A winning page test alone leaves a belief about motive unconfirmed.

Some pages won't get a comparison. How long a test needs depends on the page's traffic and on how visitors behave, as Webflow's testing documentation notes. On a page with few visitors, that can be longer than the decision can wait. The team then decides on the interviews and the observed sessions, and labels the belief with the evidence it has.

The list stays open after launch. The method's improvement cycle ends each round by learning from the data and passing the findings to marketing, sales and service. That is the point to update the assumptions. Lean Labs' growth-driven design service shows where new evidence comes from: it draws on page behavior, form and conversion behavior, CRM lifecycle stages and sales feedback. Any of those can contradict a belief that looked sound at launch.

When a belief fails, trace it back to the plan. Look again at the priorities that depended on it before you commit the next cycle's work.

Sources

Growth Driven Design: Website Strategy

GrowthDrivenDesign.com

Primary source Verified Sep 15, 2026 Supports: Methodology owner's description of the strategy stage: objectives set before tactics, customer research used to shape the site around the end customer, and an organized wishlist of ideas turned into an actionable implementation plan. Disclosure: growthdrivendesign.com is a HubSpot property, and cont

“Putting strategy before tactics enables you to take an organized wishlist of ideas and turn them into an actionable implementation plan.”

Continuous Improvement

GrowthDrivenDesign.com

Primary source Verified Sep 15, 2026 Supports: The sprint cycle of plan, build, learn, and transfer; one focus metric per plan step with the highest-impact ideas prioritized into a time-boxed build; and the transfer of learnings to marketing, sales, and service. Also the methodology's stated evidence standard for optimizations. Disclosure: growt

“Optimizations are not blind guesses. They're driven by data and proven by data.”

Growth-Driven Design for Websites

IMPACT

Supporting Verified Sep 15, 2026 Supports: Defines fundamental assumptions as the explanations of user behavior and motivation that heavily influence the next step, global and page strategy; gives the examples used here (value propositions per offer, devices and locations, information users search for); places assumptions among the six strat

“You will use these assumptions to explain user behavior and motivation, which will heavily influence the next step -- global and page strategy.”

A/B testing

Optimizely

Supporting Verified Sep 15, 2026 Supports: Definition and mechanics of a controlled comparison: a control and a variation, traffic split at random, results read through a statistical engine, with statistical significance as the test of whether a result is reliable or random chance. Also the warning that segments too small to support signific

“Statistical significance tells you if your test results are reliable or just random chance.”

Define Stronger A/B Test Variations Through UX Research

Nielsen Norman Group

Independent Verified Sep 15, 2026 Supports: Jen Cardello, April 20, 2014. Establishes that an incorrect assumption about what caused an issue produces a design variation that does not address the problem and cannot be fixed by tweaking it; that A/B testing only finds the best option among the variations available; and that user research is th

“Making incorrect assumptions about what caused an issue translates to a design variation that doesn't address the problem.”

Putting A/B Testing in Its Place

Nielsen Norman Group

Independent Verified Sep 15, 2026 Supports: Jakob Nielsen, August 14, 2005. Establishes the method's limits used here: A/B testing needs one clear goal measurable by counting user actions, so outcomes such as being placed on a shortlist for a later purchase fall outside it; it works only on fully implemented designs, which caps how many ideas

“The biggest problem with A/B testing is that you don't know why you get the measured results.”

The three stages of growth-driven design: strategy, launchpad, and continuous improvement

Lean Labs

Contributor · COI Verified Sep 15, 2026 Supports: Contributor's own practice and published ranges, used only inside the contributor perspective: HubSpot builds since 2013; ICE prioritization scored 1 to 10 on impact, confidence, and ease; a weekly or biweekly sales feedback sync; its position that sites under 1,000 visits per month will not reach s

“Each test needs to run until it reaches statistical significance. Declaring a winner after 50 visits isn't testing, it's guessing.”

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