===== 🧠 Operator Bias =====

**Operator bias** refers to systematic differences in outcomes that arise due to variations in the skill, experience, decision-making, or preferences of the individual performing a procedure or intervention.

==== ⚠️ Key Characteristics ====
  * Outcomes influenced by **who performs the procedure**, not just what is done  
  * Particularly relevant in **surgical** and **interventional** studies  
  * Often unacknowledged in retrospective analyses  
  * Can confound comparisons between techniques or centers  

==== 🧪 Example in Neurosurgery ====
  * A high-volume vascular neurosurgeon may achieve better outcomes with clipping than general neurosurgeons, skewing results in favor of surgery when comparing to endovascular treatment performed by less experienced interventionalists.

==== 📉 Why It Matters ====
  * Distorts the apparent efficacy or safety of a procedure  
  * Makes multicenter or multitechnique comparisons unreliable  
  * Introduces hidden bias in non-randomized studies  

==== ✅ Best Practice ====
  * Report operator volume and experience  
  * Perform stratified or sensitivity analyses by operator  
  * Acknowledge as a potential confounder in observational studies