EPIDEMIOLOGY PROBLEM-1
1
PROBLEMS AND SOLUTIONS
PROBLEM NUMBER 1
DIRECT & INDIRECT MORTALITY RATES
I. Using the information in the following table, calculate the crude death rates, age-specific death rates,
and adjusted death rates for Populations X and Y. Use the direct approach for age-adjusted rate
calculations.
AGE
<5
5-14
15-24
25-34
35-44
45-64
>65
TOTAL
COMMUNITY X
COMMUNITY Y
POPULATION
DEATHS
DEATH
RATE
PER 1,000
POPULATION
DEATHS
DEATH
RATE
PER 1,000
20,000
10,000
10,000
10,000
25,000
25,000
50,000
150,000
200
20
50
25
100
200
4,000
4,595
10*
2
5
2.5
4
8
80
CMRX=30.6
20,000
20,000
30,000
20,000
10,000
10,000
10,000
120,000
250
25
200
75
35
350
450
1,385
12.5
1.25
6.7
3.75
3.5
35
45
CMRY=11.5
A. Crude Mortality Rate (CMR):
CMR 
Number of Deaths
Total Population
CMR X 
4,595
 30.6
150,000
per 1,000
CMRY 
1,385
 11.5
120,000
per 1,000
B. Age-Specific Death Rates =
Number of Deaths in the Age Group
 1,000
Population in Age Group
C. Age-Adjusted Death Rate:
1. Calculate the expected deaths for each category.
2. Determine the standard population A+B or X+Y
3. Add A & B population in each category.
4. Calculate expected deaths for each category:
 Death Rate in Category 
Expected Deaths = ( S tan dard population of A & B)

1,000


 Expected Deaths 

  1,000
 Total Deaths ( A  B) 
EPIDEMIOLOGY PROBLEM-1
2
5. Calculating an Age-Adjusted Death Rate(AADR) for A & B:
AGE
<5
5-14
15-24
25-34
35-44
45-64
65+
TOTAL
AGE-ADJUSTED DEATH RATE FOR A & B
POPULATION
DEATH
EXPECTED DEATH RATE
A+B
RATE OF A
DEATH
OF B
RATE OF A
40,000
10
400
12.5
30,000
2
60
1.3
40,000
5
200
6.7
30,000
2.5
75
3.8
35,000
4
140
3.5
35,000
8
280
35
60,000
80
4,800
45
270,000
112
5,955
11.5
a. AADRA =
5,955
 1,000  22 per 1,000  2%
270,000
b. AADRB =
4,964.2
 1,000  18.38 per 1,000  2%
270,000
EXPECTED
DEATH RATE
OF B
500
37.5
266.7
112.5
122.5
1,225
2,700
4,964.2
II. Waterville County vital statistics records indicated that there were 3,790 live births in 1992,
compared to 3,334 live births in 1990. In 1992 there were 10 more neonatal deaths and 17 more infant
deaths than in 1990. In 1990 there were 70 neonatal deaths and 80 infant deaths. Calculate neonatal
and infant mortality rates (per 1,000) for Waterville Country for 1990 and 1992.
III. Use the following standard death rates to calculate standardized mortality ratios (SMR) for Green
City and Red City. How doe standardized mortality ratios compare to crude death rates for Green City
and Red City? There were 4,050 deaths in green City and 30,025 deaths in red City.
AGE
STANDARD
DEATH RATES
POPULATION
GREEN CITY
(X)
EXPECTED
DEATHS GREEN
CITY (X)
POPULATION
RED CITY (Y)
EXPECTED
DEATHS RED CITY
(Y)
<1
1-4
5-14
15-24
25-34
35-44
45-54
55-64
>65
15
1
2
1.5
1
2.5
8
10
60
6,000
7,000
7,000
7,000
10,000
10,000
13,000
15,000
25,000
100,000
90
7
14
10.5
10
25
104
150
1,500
1,910.5
50,000
75,000
25,000
30,000
70,000
25,000
20,000
20,000
20,000
335,000
750
75
50
45
70
62.5
160
200
1,200
2,612.5
TOTAL
EPIDEMIOLOGY PROBLEM-1
3
A. There are 4,050 deaths in community X (Green City). There are 30,025 deaths in community
Y (Red City).
B. Crude Mortality Rates (CMR):
1. CMRx 
Total Deaths
4,050
x 1,000  40.5
Total Population 100,000
per 1,000
2. CMRy 
Total Deaths
30,025
x 1,000  89.6
Total Population 335,000
per 1,000
3. Crude Mortality Rate does not show much—only that one is 2 times higher than the
other. More inferences can be made using the Standardized Mortality Ration (SMR).
C. Standardized Mortality Rates (SMR):
1. SMRx 
Number Observed Deaths 4,050
 2.12
Expected Deaths
1,910.5
per 1,000
2. The Green City death rate is 2 times higher than the standard rate
3. SMRY 
30,025
 11.49
2,612.5
per 1,000
4. The Red City death rate is 5 times higher than the Green City rate and 11.9 times
higher than the standard rate.