64
There are two complementary structural strategies for taking into account the
presence of the influence properties.
One strategy aims at making the measurement less and less sensitive to influence
properties, by improving the measuring instrument and overall measurement procedure. In the case of a test of reading comprehension ability, an example of an attempt
to reduce the effects of an influence property would be to deliberately write passages about a topic known to be equally unfamiliar to all examinees.
The other strategy exploits the fact that the measurand is the property intended to
be measured, and therefore that must be defined, explicitly or implicitly. The measurand could be then defined by including the specification of some environmental
conditions in the definition itself, thus changing the role of the corresponding properties, from influence properties to components of the measurand. Chapter 7
includes a discussion about the complex subject of measurand definition. For example, it might be specified that reading comprehension ability simply pertains to
one’s ability to comprehend a given set of texts regardless of whether this comprehension is based solely on semantic processing of the texts or is also aided by prior
knowledge of the content of the texts, in which case prior content familiarity is seen
as a component of reading comprehension ability rather than an influence property.
3.4 The conceptual context
For performing a measurement, in addition to the operational conditions discussed
in the previous section, some conceptual conditions also need to be fulfilled: an
existing property of an object has to be identified as the property intended to be
measured, leading to a model of the measurand, and a suitable process of property
evaluation has to be designed, leading to a model of the measurement. This last section is devoted to a preliminary discussion of these two aspects of the measurement
problem, thus setting the strategic context for the more careful and extensive analysis developed in the chapters that follow.
3.4.1 Measurement and property identification
Performing a measurement presupposes that something is there to be measured: as
previously mentioned, this is a property of an object. In most cases of mature measurement practice, both the general property and the object are well known and
clearly identified before and independently of the measurement. Given the welldeveloped status of physics, this is the usual case for measurement of physical properties: it is physics itself that guarantees that general properties such as length, mass,
and time duration are well defined, and in fact inter-defined, in a network of general
properties (and more specifically, quantities) connected by equations globally
known as the International System of Quantities (ISQ) (see ISO, 2009: 3.6; JCGM,
3 Technical and cultural contexts for measurement systems
There are two complementary structural strategies for taking into account the
presence of the influence properties.
One strategy aims at making the measurement less and less sensitive to influence
properties, by improving the measuring instrument and overall measurement procedure. In the case of a test of reading comprehension ability, an example of an attempt
to reduce the effects of an influence property would be to deliberately write passages about a topic known to be equally unfamiliar to all examinees.
The other strategy exploits the fact that the measurand is the property intended to
be measured, and therefore that must be defined, explicitly or implicitly. The measurand could be then defined by including the specification of some environmental
conditions in the definition itself, thus changing the role of the corresponding properties, from influence properties to components of the measurand. Chapter 7
includes a discussion about the complex subject of measurand definition. For example, it might be specified that reading comprehension ability simply pertains to
one’s ability to comprehend a given set of texts regardless of whether this comprehension is based solely on semantic processing of the texts or is also aided by prior
knowledge of the content of the texts, in which case prior content familiarity is seen
as a component of reading comprehension ability rather than an influence property.
3.4 The conceptual context
For performing a measurement, in addition to the operational conditions discussed
in the previous section, some conceptual conditions also need to be fulfilled: an
existing property of an object has to be identified as the property intended to be
measured, leading to a model of the measurand, and a suitable process of property
evaluation has to be designed, leading to a model of the measurement. This last section is devoted to a preliminary discussion of these two aspects of the measurement
problem, thus setting the strategic context for the more careful and extensive analysis developed in the chapters that follow.
3.4.1 Measurement and property identification
Performing a measurement presupposes that something is there to be measured: as
previously mentioned, this is a property of an object. In most cases of mature measurement practice, both the general property and the object are well known and
clearly identified before and independently of the measurement. Given the welldeveloped status of physics, this is the usual case for measurement of physical properties: it is physics itself that guarantees that general properties such as length, mass,
and time duration are well defined, and in fact inter-defined, in a network of general
properties (and more specifically, quantities) connected by equations globally
known as the International System of Quantities (ISQ) (see ISO, 2009: 3.6; JCGM,
3 Technical and cultural contexts for measurement systems