CRO Glossary
Instrumentation
The tracking code and event logging infrastructure that captures user actions so experiments can be measured accurately.
Instrumentation is the plumbing beneath every experiment: the analytics events, tags, and logging that record what a user actually did — clicked a button, viewed a page, completed a purchase — so that conversion rates and downstream metrics can be calculated at all. If instrumentation is broken or incomplete, no amount of statistical rigor in the analysis will save the test, because the underlying data is wrong.
Common instrumentation problems include double-firing events (inflating conversion counts), missing events on certain browsers or devices (undercounting a segment), and events firing before a page has fully loaded (creating SRM between control and variant if one version loads faster). These issues are often invisible until someone reconciles experiment numbers against a trusted source like backend order data.
Before trusting any experiment result, experienced teams QA the instrumentation by manually walking through both control and variant, checking that every step of the conversion funnel fires exactly once per real action, on every major browser and device the test targets. Good instrumentation hygiene is unglamorous but is consistently the difference between a trustworthy testing program and one that produces results nobody believes.
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.
See this in the wild
ABWatcher watches how top teams apply instrumentation.
Live A/B tests at 1,000+ high-converting brands, with plain-English hypothesis and takeaway.