57
example, (a) there might be a lack of clarity regarding the definition of the object
that bears the property of reading comprehension ability, insofar as it could be
(and, historically, most commonly is) a single human being in isolation, or, in the
context of contemporary sociocultural theories (e.g., Mislevy, 2018), it might be
a group of people or a single person with a given set of sociocultural resources,
which could have practical implications for issues such as whether the examinee
should be allowed access to the Internet as they read and attempt to comprehend
a text; (b) there might be a lack of clarity regarding the definition of reading
comprehension ability in general (e.g., involving questions such as these: Does it
include reading speed? Are orthographic fluency and morphemic awareness subcomponents of reading comprehension ability, or causes of it? Does reading
comprehension ability include metacognitive abilities like critical analysis of
textual information, or just “direct” comprehension?); (c) there might be a lack
of clarity regarding how the general property of reading comprehension ability is
instantiated in a given human being, if, for example, an individual is blind and
uses a text-to-speech program (is this still considered “reading”?), and so forth.
We return to a discussion of special issues faced in the human sciences in Chap.
8. The quantification of measurand definitional uncertainty is an issue that
depends on the specific context: we are not aware of any generally applicable
technique on this matter.
• Unit definitional uncertainty. Measurement is performed as a comparison
(whether direct or indirect) of the quantity of an object with a unit (the more
general case of nonquantitative properties is discussed in Chap. 6). Complementary
to measurand definitional uncertainty, the quantity unit also needs to be defined
before it can enter a comparison process, and nothing in principle prevents such
a definition from involving unit definitional uncertainty. In the 2019 edition of
the International System of units (SI) the definitional strategy is adopted of
deducing the definition of the units from the numerical values of some constant
quantities, where “the numerical values of the seven defining constants have no
uncertainty” (BIPM, 2019: p. 128; see also Sect. 6.3.4): in this case unit definitional uncertainty is zero.
• Calibration uncertainty. The relation between the unit, as defined, and the value
selected for the measurand is guaranteed by the calibration of the measurement
system, which generally cannot be assumed to be perfectly stable, resulting in a
non-null calibration uncertainty. For example, in measuring the temperature of
a body the thermometer could have been calibrated long before the measurement, and in the period since the calibration its structure might have been
changed, so that the indicated temperature no longer corresponds to the correct
one. In the case of reading comprehension ability, if different texts were being
used for different students, and these texts had different reading difficulties, then
any process that ignored these differences would be an instance of calibration
uncertainty.
• Instrumental uncertainty. Again in reference to the Basic Evaluation Equation
measurand measured value of a property
=
3.2 The quality of measurement and its results
example, (a) there might be a lack of clarity regarding the definition of the object
that bears the property of reading comprehension ability, insofar as it could be
(and, historically, most commonly is) a single human being in isolation, or, in the
context of contemporary sociocultural theories (e.g., Mislevy, 2018), it might be
a group of people or a single person with a given set of sociocultural resources,
which could have practical implications for issues such as whether the examinee
should be allowed access to the Internet as they read and attempt to comprehend
a text; (b) there might be a lack of clarity regarding the definition of reading
comprehension ability in general (e.g., involving questions such as these: Does it
include reading speed? Are orthographic fluency and morphemic awareness subcomponents of reading comprehension ability, or causes of it? Does reading
comprehension ability include metacognitive abilities like critical analysis of
textual information, or just “direct” comprehension?); (c) there might be a lack
of clarity regarding how the general property of reading comprehension ability is
instantiated in a given human being, if, for example, an individual is blind and
uses a text-to-speech program (is this still considered “reading”?), and so forth.
We return to a discussion of special issues faced in the human sciences in Chap.
8. The quantification of measurand definitional uncertainty is an issue that
depends on the specific context: we are not aware of any generally applicable
technique on this matter.
• Unit definitional uncertainty. Measurement is performed as a comparison
(whether direct or indirect) of the quantity of an object with a unit (the more
general case of nonquantitative properties is discussed in Chap. 6). Complementary
to measurand definitional uncertainty, the quantity unit also needs to be defined
before it can enter a comparison process, and nothing in principle prevents such
a definition from involving unit definitional uncertainty. In the 2019 edition of
the International System of units (SI) the definitional strategy is adopted of
deducing the definition of the units from the numerical values of some constant
quantities, where “the numerical values of the seven defining constants have no
uncertainty” (BIPM, 2019: p. 128; see also Sect. 6.3.4): in this case unit definitional uncertainty is zero.
• Calibration uncertainty. The relation between the unit, as defined, and the value
selected for the measurand is guaranteed by the calibration of the measurement
system, which generally cannot be assumed to be perfectly stable, resulting in a
non-null calibration uncertainty. For example, in measuring the temperature of
a body the thermometer could have been calibrated long before the measurement, and in the period since the calibration its structure might have been
changed, so that the indicated temperature no longer corresponds to the correct
one. In the case of reading comprehension ability, if different texts were being
used for different students, and these texts had different reading difficulties, then
any process that ignored these differences would be an instance of calibration
uncertainty.
• Instrumental uncertainty. Again in reference to the Basic Evaluation Equation
measurand measured value of a property
=
3.2 The quality of measurement and its results