This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Screening, Subject name: Social & Preventive Medicine
Which one of the following will be affected by inter observer variation in epidemiological studies- 
Select and explain. 
A. Sensitivity, B. Predictive value of the positive test, C. Specificity, D. Reliability
D: Reliability
Answer: D: Reliability 
Explanation: ref: Park&;s 23rd edition pg 138 Reliability / repeatablility / Precision: that is test must give consistent results when repeated more than once on the same individual or material, under same conditions. Reliability of a test depends on 3 major factors: Observer variation (intra and inter) Biological variation Errors relating to technical methods.