CRO Glossary
Conversion Rate
The percentage of visitors who complete a desired action, such as a purchase or signup.
Conversion rate is the core metric of CRO: the number of conversions divided by the number of visitors (or sessions), expressed as a percentage. If 500 out of 10,000 visitors buy something, the conversion rate is 5%. Everything in experimentation ultimately exists to move this number, or a related one, in the right direction.
The tricky part is defining "conversion" correctly for the test at hand. A test might target micro-conversions (adding to cart, starting a form) as well as the macro-conversion (completed purchase). Optimizing a micro-conversion without checking the macro-conversion can backfire — for instance, a flashier "Add to Cart" button might increase cart adds but not actual purchases, which is why teams pair conversion rate with a guardrail metric like revenue per visitor.
Conversion rate should always be read alongside sample size and confidence. A jump from 5% to 6% based on 40 visitors is noise; the same jump based on 40,000 visitors is a real signal worth acting on.
Related terms
Above vs Below Median Split
A segmentation technique that divides users into two groups at the median of a metric to compare high and low engagers.
Qualitative Feedback Loop
A recurring process of collecting and acting on user comments, session recordings, and survey responses to inform test hypotheses.
Experiment Metadata
The structured record of who, what, when, and how for a test — hypothesis, owner, dates, variants, and metrics used to track and audit it.
Pre-Test Analysis
The upfront work of validating traffic, metrics, and baseline data quality before launching an experiment.
Above-the-Fold vs Below-the-Fold Messaging Hierarchy
How the order and prominence of value-proposition messaging is split between the visible screen and the rest of the page.
Experiment Contamination
When a control or variant group is unintentionally exposed to the other condition, corrupting the comparison.
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