Basic statistic (1)

Data
- Qualitative
   Nominal : ABO blood group, male/female, dead/alive
   Ordinal  : mild/moderate/severe
- Quantitative
   Numerical discrete : number of death per year
   Numerical continuous: age, weight, blood pressure


Sensitivity
- probability that a test will be positive when a patient has the condition (TP / TP+FN)


Specificity
- probability that a test will be negative when a patient does not have the condition (TN / TN+FP)
- if threshold for screening is increased, specificity will increase


Positive predictive value
- probability that if a test is positive, it is true (TP/ TP+FP)


Negative predictive value
-  probability that if a test is negative, it is true (TN / TN+FN)


   The higher prevalence will have greater PPV and lower NPV