Progression
Progression, like progress, is about moving from where you are by
steps.
In mathematics, a progression is a series of numbers that increases
or decreases by steps. The steps are
proportional
to one another. Different kinds of progression have different proportions.
Arithmetic Progression
An example of an arithmetic progression is:
1, 4, 7, 10, 13, 16, 19, 22, 25.....
Geometric Progression
An example of geometric progression is:
1, 4, 16, 64, 256, 1,024.....
Proportion
The proportion or ratio that one number bears to another is the
result
of dividing one by the other.
For example,
The proportion of 3 to 7 is three divided by seven = 0.42
The proportion of 6 to 14 is six divided by fourteen
This is also 0.42
Any number divided into itself is one. So the ratio of a quantity to the
same quantity of something else is one. Look at
the graph of the
British balance of trade. This has the ratio
of export to import volumes as its vertical axis. When exports and imports
are equal, the ratio is one.
A rate is often a ratio: the quantity of something expressed
as a proportion. For example, Durkheim defines the
rates of births, marriages, and suicides as
"
the number obtained by dividing the average annual total of marriages,
births, suicides, by the number of persons whose ages lie within the range
in which marriages, births, and suicides occur."
Parsons distinguishes between rates and incidence
A frequent use of rates in
statistics is to construct
time series showing the rate of change over time
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