Expected Impact
What is expected impact?
Expected impact is a critical component of a good hypothesis that defines what specific, measurable outcome you expect to see as a result of making a change—including by how much. It's not enough to say a redesign will "increase usability." You need to specify which metric you expect to be affected (like reducing time to complete an action or increasing customer satisfaction) and estimate the magnitude of change (like "increase conversion rate from 10% to 15%").
Defining expected impact serves two key purposes: it helps you draw a line in the sand to determine whether your hypothesis passes or fails, and it allows you to calculate how long to run your test.
Why does defining expected impact matter?
It's easy to generate product ideas. It's much harder to understand the impact you expect each idea to have. But it's important that you do so. If you don't, you can waste countless hours testing ideas that don't matter.
Defining expected impact also protects you from your own biases down the road. It's very easy after the fact to determine that a 9% improvement is good enough when you predicted 10%. Or that 2% is good enough. Or that -2% is okay because you like the change. Without a line in the sand, you're setting yourself up to ignore your data.
When you define by how much you expect the change to impact your metric, your hypothesis should determine in black and white terms whether it passes or fails and should dictate how you act on the results.
How do you estimate expected impact?
Start with your baseline. If you're trying to improve your conversion rate, know what your conversion rate is today. A 50% increase is much easier when your conversion rate is 10% than when it's 40%, and it's impossible when it's 80%.
Look at comparable product changes. Find similar changes you've made in the past and understand what impact they had. Over time, you'll build up your knowledge base of how much impact different types of product changes tend to have.
Assess how much impact makes the investment worthwhile. Ask yourself: "How much impact do I need to see to make this change worth it?" Consider the cost of implementation, opportunity cost, and ongoing maintenance.
Learn more:
- The 5 Components of a Good Hypothesis
- How to Estimate the Expected Impact of a Product Change
Related terms:
- Line in the Sand
- Hypothesis
- Assumption Testing
- Experiments
- Metrics
Last Updated: October 25, 2025