trying to find the domain and the range of the functionsthe project is about scatter plots years of 1980-2008 deaths from 16-90

The domain of a relation (or a function) is the set of
inputs. It is typically the independent variable, and is graphed along the
x-axis.

If the data is listed as ordered pairs with year
first followed by number of deaths (e.g. (1988,1267)) then the input is the year; the
output is the number of deaths. If the data is the number of deaths by age per year,
then the input is the age. It is unclear from your question how the data are
listed.

So if the data is listed (year, number of deaths)
then the domain is the set of years you are looking at:{1980,1981,...,2008}. If the data
is listed as number of deaths per age (e.g.(16,134) means 134 people age 16 died) then
the domain is the ages you are interested in:
{16,17,...,90}

The range is the set of all outputs -- in
either case above the range is the set of the different number of
deaths.

If your data set is finite, then you can list both
domain and range as sets. For a large data set, you can define the domain and range as
intervals or inequalities: domain 1980<y<2008 with y a whole number year
and the range as (smallest number of deaths)<d<(largest number of deaths)
where d is a whole number of deaths.