This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Social & Preventive Medicine
L-J chart is used for monitoring -a)  Accuracyb)  Precisionc)  Sensitivityd)  Specificity 
Select and explain. 
A. ac, B. ab, C. ad, D. bc
C: ad
Answer: C: ad 
Explanation: The formulation of Westgard rules were based on statistical methods. 
Westgard rules are commonly used to analyse data in Shewhart control Charts Westgard rules are used to define specific performance limits for a particular assay and can beused to detect both random and systematic errors.