Measuring health and illness

Measures of Disease Frequency: Basic Measures

Sample Numeric Calculations

Calculations are for some specified time period.

1. Calculating a Proportion

# Deaths

Population

Whites

20,000

220,000,000

Nonwhites

14,000

125,000,000

    TOTAL

34,000

345,000,000

  • Question: What proportion of all deaths is by those who are white?
  • Answer:  20,000 / 34,000  =  0.588 (i.e., 58.5%)

Note: numerator (whites who died) are included in denominator (total # deaths)

2. Calculating a Ratio

# Deaths

Population

Whites

20,000

220,000,000

Nonwhites

14,000

125,000,000

    TOTAL

34,000

345,000,000

  • Question: How do deaths among whites compare to deaths among nonwhites (i.e., what is ratio of white deaths to nonwhite deaths)?
  • Answer
    • White deaths = 20,000; Nonwhite deaths = 14,000
    • White deaths compared to nonwhite deaths = 20,000 / 14,000  =  1.43

Interpretation: 1.43 white deaths for every nonwhite death

3. Calculating a Rate

# Deaths

Population

Whites

20,000

220,000,000

Nonwhites

14,000

125,000,000

    TOTAL

34,000

345,000,000

  • Question: what is overall mortality rate?
  • Answer: Total # deaths = 34,000.  Total population = 345,000,000

Mortality rate = 34,000 / 345,000,000  =  0.0000986

  • Multiply by 1,000 for rate per 1,000 (0.0986 deaths per 1,000 population)
  • Multiply by 1,000,000 for rate per 1 million (98.6 deaths per 1 million population)

 

4. Calculating a Rate

# Deaths

Population

Whites

20,000

220,000,000

Nonwhites

14,000

125,000,000

    TOTAL

34,000

345,000,000

  • Question: what is the race-specific mortality rate?
  • Answer:

                Among Whites20,000 / 220,000,000 = 0.0000909

                Among Nonwhites: 14,000 / 125,000,000 = 0.000112

Mortality rates per million population:

– mortality rate among whites = 90.9  per million

– mortality rate among nonwhites = 112.0 per million