Positive and Negative Predicted Values

 3. Positive Predictive Value (PPV):

• Definition: PPV is the probability that individuals with a positive test result actually have the disease.
• Calculation: PPV = (True Positives) / (True Positives + False Positives)
• Interpretation: A high PPV indicates that a positive test result is a good indicator of the presence of the disease.

Example: If 80 out of 100 people with a positive test result actually have the disease, the PPV is 80%.

4. Negative Predictive Value (NPV):

• Definition: NPV is the probability that individuals with a negative test result do not have the disease.
• Calculation: NPV = (True Negatives) / (True Negatives + False Negatives)
• Interpretation: A high NPV indicates that a negative test result is a good indicator of the absence of the disease.

Example: If 90 out of 100 people with a negative test result do not have the disease, the NPV is 90%.

5. Prevalence:

• Definition: Prevalence is the proportion of individuals in a population who have a specific disease at a given time.
• Calculation: Prevalence = (Number of cases of the disease) / (Total population)

Example: If there are 50 cases of a disease in a population of 1,000, the prevalence is 5%.