c. What is required.
The principles of statistics outline ways in
which samples may be taken, how large a sampling is required, and the type
of averages that are appropriate to particular situations. All these items
will be discussed in due time.
First, however, examine some pertinent
definitions.
d. Definitions.
(1) Population.
The total things, events, or quantities under
consideration. The size and extent of the population should be described.
EXAMPLE. All
the workshoes in Kansas or all the golf clubs sold in Oregon.
Each item of
the population as a whole has characteristics (for example,
length). The
population as a whole has characteristics of characteristics
(for example,
the average length).
(2) Parameter. Some characteristic of the population. Generally, a
parameter is some truth about the population that we are trying to discover
(as accurately as possible) by means of sampling and statistical
manipulation.
(3) Sample. A group drawn from the population. Obviously, we cannot
examine all the workshoes in Kansas, but if we would select a random sample,
of 10 shoes from each county, the average length of the sample would be a
good guess as to the average length of all the shoes. To avoid confusion,
sometimes the group is called a sampling, and each unit of it is referred to
as a sample.
(4) Statistic. Some calculated value derived from a sampling. This
is an estimate of some corresponding value pertaining to the population.
How good an estimate it is depends on the nature and size of the population,
the way in which the sampling was taken, and the statistics computed.
(5) Data. A group of facts or statistics; often used with a singular
verb. This word is the plural of datum, which in a statistical sense means
a particular value or fact.
(6) Observation.
In a scientific sense, this is considered to be the
gathering of data.
e. Observation.
(1) This is the source of practically all objective data. Usually,
it is obtained with the aid of some measuring device. There is very little
subjectivity connected with the reading of the device, since, when it is
used properly, different people will get the same readings under the same
set of conditions.
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