Don't just focus on successful outcomes, failures are equally informative.
Definition
Survivorship bias is a logical error of concentrating on the people or things that made it past some selection process and overlooking those that did not, typically because of their lack of visibility. In UX design, this could mean only considering successful user interactions and ignoring instances where users struggled or failed to complete tasks.
Do
Consider both successful and unsuccessful user interactions when making design decisions
Analyze why certain parts of a design failed and how they can be improved
Use both positive and negative data to inform future design iterations
Avoid
Don't ignore or dismiss failures as outliers or irrelevant
Don't base design decisions solely on successful outcomes
Don't overlook the importance of learning from unsuccessful designs or features
When to apply
When analyzing user behavior data
When iterating on existing designs
When evaluating the usability of a product or feature