Chapter 15 Human Ecology • MHR 5095.Calculate the mortality rate (the proportion of the
population that died) for the first age interval. Then
standardize the data from each group to a cohort of
- For example, if records for 200 deaths were
obtained and 90 of these involved children less than
five years of age, then the mortality rate equals the
number of deaths per cohort in that age group.
Multiplying this number by 1000 then gives you the
number that would have died if you had a cohort of
1000, thus standardizing the data to this cohort
size. For this example, the calculations would be:
90
200
=0.450
0.450× 1000 = 450
6.Survivorship is described as the proportion of the
total population surviving through an age interval
and therefore alive at the start of the next interval.
The survivorship at the start of the first age interval
is 100 percent, since all members of the cohort are
assumed to be alive at the start of the exercise.
The proportion surviving through this interval (and
therefore alive at the start of the second age interval)
is one minus the mortality rate for the first interval.
For the example given above, the survivorship for
individuals in the zero to just under five interval
would be:
1 −^450
1000
= 1 −0.450
=0.550
The number surviving out of the original standardized
cohort (of 1000) would be 0.550× 1000 = 550.7.Calculate the mortality through the next age interval
as in step 5. For example, if 50 of the 200 people in
your sample died between the ages of five and just
under 10 years of age, the mortality rate for this
interval is:
50
200
=0.250
0.250× 1000 = 250
To calculate the survivorship through this interval,
this interval’s mortality rate must be subtracted
from the proportion of the population alive at the
beginning of this age interval. This proportion is the
same as the survivorship through the previous age
interval as determined in step 6. The survivorship for
this interval would then be:
550
1000−^250
1000
=0.550−0.250
=0.300
0.300× 1000 = 300
8.Calculate the mortality and survivorship rates for
each subsequent age interval using the method
described in steps 5 to 7.
9.Each group should construct a curve showing the
pattern of survivorship for the males or females who
died during a given time interval. This graph should
have survivorship on the y-axis and age intervals on
the x-axis. Survivorship can be expressed either as
proportions or actual numbers, so the y-axis can
extend from 0 to 1 or from 0 to 1000.Post-lab Question
1.Describe the shape of your group’s survivorship
curve. Does it seem most similar to a Type I, II, or III
survivorship curve (refer to Chapter 14, section 14.4)?Conclude and Apply
2.Compare the curves for different sexes and time
periods. Were your predictions about potential
differences in the survivorship patterns at different
historical times correct? Describe any differences
between your predictions and what you actually
observed.
3.Explain the differences you see between historical
periods with respect to survivorship patterns.
4.Were there any differences between the sexes with
respect to their survivorship patterns in a particular
time period and/or age interval? If so, explain why
these differences might exist.
5.Do you think there might be differences among
cemeteries in different regions (for example, urban
versus rural) or between different parts of a city with
respect to the survivorship patterns of people who
died during certain eras? Explain your answer.
6.Do you think your data provided an accurate picture
of survivorship in your area? What might you do to
get a clearer picture?Exploring Further
7.If the data are available, calculate the proportion of
individuals in each time interval who died from as
many of the following general categories of causes
as possible.
(a)stillborn
(b)accident
(c)infectious diseases (that is, contagious diseases
caused by a bacteria, virus, or other type of
parasitic organism)
(d)degenerative diseases (for example, cancer,
heart disease, stroke)
(e)other
Use a bar graph or pie chart to illustrate your
results. Is there a difference among the time
intervals with respect to the proportion of individuals
in each of these categories? Relate any differences
you see to historical developments within your
community (for example, wars, the installation of
water treatment plants, hospital construction, and
so forth).