|
|
| Examples
taken from Mausner & Bahn (1974) |
Annual
Age-Specific
Death Rate
per 1000 |
Annual
Number
of Deaths |
Crude
Death
Rate
per 1000 |
|
|
Age
(Years) |
Population |
| Number |
Proportion |
|
|
| |
|
|
|
|
|
45
/ 5000
= 9.0 |
| Population
A |
<
15 |
1500 |
.30 |
2 |
3 |
| |
15-44 |
2000 |
.40 |
6 |
12 |
| 45
+ |
1500 |
.30 |
20 |
30 |
| All
Ages |
5000 |
1.00 |
|
45 |
| |
| Population
B |
<
15 |
2000 |
.40 |
2 |
4 |
29
/ 5000
= 5.8 |
| |
15-44 |
2500 |
.50 |
6 |
15 |
| |
45
+ |
500 |
.10 |
20 |
10 |
| |
All
Ages |
5000 |
1.00 |
|
29 |
|
|
| In
the example above, the absolute numbers of deaths and the crude
death rates of Population A and Population B
differ considerable (45 versus 29; 9.0 per 1000 as opposed to 5.8 per
1000). However, note that the age-specific
death rates are identical. Standardization
of the rates will adjust for differences in population structure.
In the example below, the age-specific death rates (as in the example
above) are identical. |
|
|
| Computation
of expected number of deaths by the direct method. In this
example, the populations have IDENTICAL age-specific death rates. |
| Age
(Years) |
Standard
Population
(A & B Combined) |
Population
A
Age-specific Death
Rates per 1000 |
Expected
Deaths |
Population
B
Age-specific Death
Rates per 1000 |
Expected
Deaths |
|
| |
(1) |
(2) |
(3)
= (2) X (1) |
(4) |
(5)
= (4) X (1) |
| <
15 |
3500 |
2 |
7 |
2 |
7 |
| 15-44 |
4500 |
6 |
27 |
6 |
27 |
| 45
+ |
2000 |
20 |
40 |
20 |
40 |
| All
Ages |
10,000 |
|
74 |
|
74 |
| |
|
|
74
/ 10,000
= 7.4 per 10000 |
|
74
/ 10,000
= 7.4 per 10000 |
| |
|
|
|
| Direct
standardization tells us the that differences in the crude rates (and
numbers of death) are expected from the differences in population
structure. |
|
|
| Computation
of expected number of deaths by the direct method. In this
example, the populations have DIFFERENT age-specific death rates. |
| Age
(Years) |
Standard
Population
(A & B Combined) |
Population
A
Age-specific Death
Rates per 1000 |
Expected
Deaths |
Population
B
Age-specific Death
Rates per 1000 |
Expected
Deaths |
|
| |
(1) |
(2) |
(3)
= (2) X (1) |
(4) |
(5)
= (4) X (1) |
| <
15 |
3500 |
2 |
7 |
2 |
7 |
| 15-44 |
4500 |
6 |
27 |
10 |
45 |
| 45
+ |
2000 |
20 |
40 |
20 |
40 |
| All
Ages |
10,000 |
|
74 |
|
92 |
| |
|
|
74
/ 10,000
= 7.4 per 10000 |
|
92
/ 10,000
= 9.2 per 10000 |
| |
|
|
|
| In
this example, we see how differences in the age-specific rate are
evident in the adjusted rates. Had the age-specific rates
been identical, the adjusted rates would have been identical. In real
world populations, the age-specific rate will vary from population to
population (These may or may not be significant.)
Standardization of the rates provides a summary of the event that can
be used to evaluate those differences. Review
the advantages and disadvantages of the types of rates. |
|
|