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Measurement is the
process observing and recording the
observations that are collected as part of a
research effort. There are two major issues that will be considered here.
In classical physics and engineering, measurement generally
refers to the process of estimating or determining the ratio
of a magnitude of a quantitative property or relation to a
unit of the same type of quantitative property or relation.
A process of measurement involves the comparison of physical
quantities of objects or phenomena, or the comparison of
relations between objects (e.g. angles). A particular
measurement is the result of such a process, normally
epxressed as the multiple of a real number and a unit, where
the real number is the ratio obtained from the measurement
process. For example, the measurement of the
length of an
object might be 5 m, which is an estimate of the object's
length, a magnitude, relative to a unit of length, the meter.
Measurement is not limited to physical quantities and
relations but can in principle extend to the quantification
of a magnitude of any type, through application of a
measurement model such as the Rasch model, and subjecting
empirical data derived from comparisons to appropriate
testing in order to ascertain whether specific criteria for
measurement have been satisfied.
In addition, the term mesurement is often used in a somewhat
looser fashion than defined above, to refer to any process
in which numbers are assigned to entities such that the
numbers are intended to represent increasing amount, in some
sense, without a process that involves the estimation of
ratios of magnitudes to a unit. Such examples of measurement
range from degrees of uncertainty to consumer confidence to
the rate of increase in the fall in the price of a good or
service. It is generally proposed that there are four
different levels of measurement, and that different levels
are applicable to different contexts and types of
measurement process.
In scientific research, measurement is essential. It
includes the process of collecting data which can be used to
make claims about learning. Measurement is also used to
evaluate the effectiveness of a program or product (known as
an evaluand).
First, you have to understand the fundamental ideas involved
in measuring. Here we consider two of major measurement
concepts. In Levels of Measurement, I explain the meaning of
the four major levels of measurement: nominal, ordinal,
interval and ratio. Then we move on to the reliability of
measurement, including consideration of true score theory
and a variety of reliability estimators.
Second, you have to understand the different types of
measures that you might use in social research. We consider
four broad categories of measurements. Survey research
includes the design and implementation of interviews and
questionnaires. Scaling involves consideration of the major
methods of developing and implementing a scale. Qualitative
research provides an overview of the broad range of
non-numerical measurement approaches. And unobtrusive
measures presents a variety of measurement methods that
don't intrude on or interfere with the context of the research.
Americans probably use a greater variety of
units of
measurement than anyone else in the world. Caught in a
slow-moving transition from customary to
metric units, we
employ a fascinating and sometimes frustrating mixture of
units in talking about the same things. We measure the
length of a race in meters, but the length of the long jump
event in feet and inches. We speak of an engine's power in
horsepower and its displacement in liters. In the same
dispatch, we describe a hurricane's wind speed in knots and
its central pressure in millibars.
Furthermore, our English customary units do not form a
consistent system. Reflecting their diverse roots in Celtic,
Roman, Saxon, and Norse cultures, they aoften confusing
and contradictory. There are two systems for land
measurement (one
based on the yard and the other on the rod)
and a third system for distances at sea. There are two
systems (avoirdupois and troy) for small weights and two
more (based on the long and short tons) for large weights.
Americans use two systems for volumes (one for dry
commodities and one for liquids) and the British use a third
(British Imperial Measure).
Meanwhile, only a few Americans know that the legal
definitions of the English customary units are actually
based on metric units. The U. S. and British governments
have agreed that a yard equals exactly 0.9144 meter and an
avoirdupois pound equals exactly 0.453 592 37 kilograms. In
this way, all the units of measurement Americans use every
day are based on the standards of the metric system. Since
1875, in fact, the United States has subscribed to the
International System of Weights and Measures, the official
version of the metric system.
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