When you have a hypothesis and want to Validate your learning one could even offer a MVP or fake prototype and see how potential or actual customers interact with this.
You still need to be aware that metrics only capture things that can be quantified.
Reference
Ries, Eric. The Lean Startup: How Today’s Entrepreneurs Use Continuous Innovation to Create Radically Successful Businesses. 1st ed, Crown Business, 2011.
Highlights or timestamps
Don’t use questionnaires or fictional customers though; instead, talk to real customers in a realistic environment. The most reliable way to find out whether people will buy your product is to offer it to them and see how they respond.
— ^94d35d from The Lean Startup