Health professionals use numbers a lot when studying health issues. This helps them understand how different factors affect people's health.

1. Incidence and Prevalence Ratios:

   • The incidence rate shows how many new cases of a disease appear over time. To find this, you divide the number of new sick people by the number of people at risk. For example, if 50 new people get a disease in a group of 10,000, you calculate it like this:
     [ \frac{50}{10,000} = 0.005
     ]
     This means there are 500 new cases for every 100,000 people.
   • The prevalence ratio tells us how common a disease is at a certain point in time. If 200 people out of 10,000 have a disease, it would look like this:
     [ \frac{200}{10,000} = 0.02
     ]
     This means 2% of that group is affected.

2. Risk Ratios:

   • This ratio compares how likely health problems are between two groups. For instance, if 30% of smokers get lung cancer and only 10% of non-smokers do, we can calculate the risk ratio:
     [ \frac{30%}{10%} = 3
     ]
     This shows that smokers are three times more likely to get lung cancer than non-smokers.

3. Mortality Ratios:

   • The mortality ratio looks at how many people die in a specific group compared to the total population. For example, if there are 300 deaths in a group of 1,000 people, it can be calculated like this:
     [ \frac{300}{1,000} = 0.3
     ]
     This means 30% of that group has died.

These ratios help doctors and health experts understand and address health issues more effectively.