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Criteria for Good Measurement
Sushant Kumar Sinha
Sushovan Bej
Criteria for good measurements?
“The use of better instrument will ensure more
accuracy in results, which in turn, will enhance the
scientific quality of the research”
There are three measurement of the characteristics for
evaluating a measurement tool.
1. Validity
2. Reliability
3. Sensitivity
Validity
It is the ability of an instrument to measure what it is
supposed to measure.
That is, when we ask a questions with the hope that we
are tapping the concept, how can we be reasonably
certain that we are indeed measuring the concept we
set out to do and not something else?
Establishing Validity
Researcher have attempted to assess validity in many ways.
They attempt to provide some evidence of a measure’s
degree of validity by answering a variety of questions
There are four basic approaches to establishing validity are
widely classified as following
1. Face Validity
2. Content Validity
3. Criterion-Related Validity
4. Construct Validity
Face Validity
It is considered as a basic and very minimum index of content validity.
It indicates that the items that are intended to measure a concept, do
on the face of it look like they measure the concept.
For e.g. a few people would accept a measure of college student math
ability using a question that asked students: 2 + 2 = ? This is not a valid
measure of collegelevel math ability on the face of it.
Nevertheless, it is a subjective agreement among professionals that a
scale logically appears to reflect accurately what it is supposed to
measure. When it appears evident to experts that the measure provides
adequate coverage of the concept, a measure has face validity
Continued…
Clear, understandable questions such as “How many children do you
have?” generally are agreed to have face validity. But it becomes more
difficult to assess face validity in regard to more complicated
business phenomena.
For instance, consider the concept of customer loyalty. Does the
statement “I prefer to purchase my groceries at Delavan Fine Foods”
appear to capture loyalty? How about “I am very satisfied with my
purchases from Delavan Fine Foods”? What about “Delavan Fine
Foods offers very good value”? While the first statement appears to
capture loyalty, it can be argued the second question is not loyalty
but rather satisfaction. What does the third statement reflect? Do we
think it looks like a loyalty statement?
Content Validity
The content validity of a measuring instrument is the
extent to which it provides adequate coverage of the
investigate questions guiding the study. If the
instrument contains a representative sample of the
universe of subject matter of the interest, then the
content validity is good.
To put it differently, content validity is a function of
how well the dimensions and elements of a concept
have been delineated
Continued…
Look at the concept of feminism which implies a person's
commitment to a set of beliefs creating full equality between men and
women in areas of the arts, intellectual pursuits, family, work, politics,
and authority relations. Does this definition provide adequate coverage
of the different dimensions of the concept?
Then we have the following two questions to measure feminism:
1. Should men and women get equal pay for equal work?
2. Should men and women share household tasks?
These two questions do not provide coverage to all the dimensions
delineated earlier. It definitely falls short of adequate content validity
for measuring feminism
CriterionRelated Validity
Criterion validity uses some standard or criterion to
indicate the a construct accurately. The validity of an
indicator is verified by comparing it with another
measure of the same construct in which research has
confidence.
There are two subtypes of this kind of validity
1. Concurrent Validity
2. Predictive Validity
Concurrent Validity
To have concurrent validity, an indicator must be associated with
a preexisting indicator that is judged to be valid.
For e.g. we create a new test to measure intelligence. For it to be
concurrently valid, it should be highly associated with existing
IQ tests (assuming the same definition of intelligence is used). It
means that most people who score high on the old measure
should also score high on the new one, and vice versa.
The two measures may not be perfectly associated, but if they
measure the same or a similar construct, it is logical for them to
yield similar results.
Predictive Validity
Criterion validity whereby an indicator predicts future events that are
logically related to a construct is called a predictive validity. It cannot be
used for all measures. The measure and the action predicted must be
distinct from but indicate the same construct. Predictive measurement
validity should not be confused with prediction in hypothesis testing,
where one variable predicts a different variable in future.
For e.g. looking at the scholastic assessment tests being given to candidates
seeking admission in different subjects. These are supposed to measure the
scholastic aptitude of the candidates the ability to perform in institution as
well as in the subject. If this test has high predictive validity, then
candidates who get high test score will subsequently do well in their
subjects. If students with high scores perform the same as students with
average or low score, then the test has low predictive validity
Construct Validity
Construct validity is for measures with multiple indicators.
It addresses the question: If the measure is valid, do the
various indicators operate in consistent manner? It
requires a definition with clearly specified conceptual
boundaries. In order to evaluate construct validity, we
consider both theory and the measuring instrument being
used.
There are two subtypes of this kind of validity
1. Convergent Validity
2. Discriminant Validity
Convergent Validity
Convergent validity means that multiple measures of the
same construct hang together or operate in similar ways.
For e.g. we construct "education" by asking people how
much education they have completed, looking at their
institutional records, and asking people to complete a test
of school level knowledge. If the measures do not converge
(i.e. people who claim to have college degree but have no
record of attending college, or those with college degree
perform no better than high school dropouts on the test),
then our test has weak convergent validity and we should
not combine all three indicators into one measure.
Discriminant Validity
Also called Divergent validity, discriminant validity is the
opposite of convergent validity. It means that the indicators of
one construct hang together or converge, but also diverge or are
negatively associated with opposing constructs. It says that if two
constructs A and B are very different, then measures of A and B
should not be associated.
For example, we have 10 items that measure political
conservatism. People answer all 10 in similar ways. But we have
also put 5 questions in the same questionnaire that measure
political liberalism. Our measure of conservatism has
discriminant validity if the 10 conservatism items hang together
and are negatively associated with 5 liberalism ones.
Reliability
The reliability of a measure indicates the extent to
which it is without bias (error free) and hence ensures
consistent measurement across time and across the
various items in the instrument.
In other words, the reliability of a measure is an
indication of the stability and consistency with
which the instrument measures the concept and helps
to assess the “goodness” of measure
Stability
The ability of the measure to remain the same over
time despite uncontrollable testing conditions or the
state of the respondents themselves is indicative of its
stability and low vulnerability to changes in the
situation.
This attests to its "goodness" because the concept is
stably measured, no matter when it is done.
Two tests of stability are testretest reliability and
parallelform reliability
Test-Retest Reliability
Testretest method of determining reliability involves administering the same
scale to the same respondents at two separate times to test for stability. If the
measure is stable over time, the test, administered under the same conditions
each time, should obtain similar results.
For example, suppose a researcher measures job satisfaction and finds that 64
percent of the population is satisfied with their jobs. If the study is repeated a
few weeks later under similar conditions, and the researcher again finds that 64
percent of the population is satisfied with their jobs, it appears that the
measure has repeatability.
The high stability correlation or consistency between the two measures at
time 1 and at time 2 indicates high degree of reliability. This was at the
aggregate level; the same exercise can be applied at the individual level. When
the measuring instrument produces unpredictable results from one testing to
the next, the results are said to be unreliable because of error in measurement.
ParallelForm Reliability
When responses on two comparable sets of measures
tapping the same construct are highly correlated, we have
parallelform reliability. It is also called equivalentform
reliability.
Both forms have similar items and same response format,
the only changes being the wording and the order or
sequence of the questions. What we try to establish here is
the error variability resulting from wording and ordering of
the questions. If two such comparable forms are highly
correlated, we may be fairly certain that the measures are
reasonably reliable, with minimal error variance caused by
wording, ordering, or other factors.
Internal Consistency of Measure
Internal consistency of measures is indicative of the
homogeneity of the items in the measure that tap the
construct.
In other words, the items should `hang together as a set'
and be capable of independently measuring the same
concept so that the respondents attach the same overall
meaning to each of the items. This can be seen by
examining if the items and the subsets of items in the
measuring instrument are highly correlated. Consistency
can be examined through the interitem consistency
reliability and splithalf reliability.
Inter-item Consistency reliability
This is a test of consistency of respondent’s
answers to all the items in a measure. To the degree
that items are independent measures of the same
concept, they will be correlated with one another
Split-Half Reliability
It reflects the correlation between two halves of an
instrument. The estimates could vary depending on how
the items in the measure are split into two halves.
The technique of splitting halves in the most basic method
for checking internal consistency when measures contain a
large number of items. In the split-half method the
researcher may take the results obtained from one half of
the scale items(e.g. odd-numbered items) and check them
against the results from the other half of the items (e.g.
even numbered items). The high correlation tells us there
is similarity (or homogeneity) among its items.
Reliability vs Validity
Reliability is a necessary but not sufficient condition
for validity. A reliable scale may not be valid.
For example, a purchase intention measurement
technique may consistently indicate that 20 percent of
those sampled are willing to purchase a new product.
Whether the measure is valid depends on whether 20
percent of the population indeed purchases the
product. A reliable but invalid instrument will yield
consistently inaccurate results
Reliablity and Validity

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Reliablity and Validity

  • 1. Criteria for Good Measurement Sushant Kumar Sinha Sushovan Bej
  • 2. Criteria for good measurements? “The use of better instrument will ensure more accuracy in results, which in turn, will enhance the scientific quality of the research” There are three measurement of the characteristics for evaluating a measurement tool. 1. Validity 2. Reliability 3. Sensitivity
  • 3. Validity It is the ability of an instrument to measure what it is supposed to measure. That is, when we ask a questions with the hope that we are tapping the concept, how can we be reasonably certain that we are indeed measuring the concept we set out to do and not something else?
  • 4. Establishing Validity Researcher have attempted to assess validity in many ways. They attempt to provide some evidence of a measure’s degree of validity by answering a variety of questions There are four basic approaches to establishing validity are widely classified as following 1. Face Validity 2. Content Validity 3. Criterion-Related Validity 4. Construct Validity
  • 5. Face Validity It is considered as a basic and very minimum index of content validity. It indicates that the items that are intended to measure a concept, do on the face of it look like they measure the concept. For e.g. a few people would accept a measure of college student math ability using a question that asked students: 2 + 2 = ? This is not a valid measure of collegelevel math ability on the face of it. Nevertheless, it is a subjective agreement among professionals that a scale logically appears to reflect accurately what it is supposed to measure. When it appears evident to experts that the measure provides adequate coverage of the concept, a measure has face validity
  • 6. Continued… Clear, understandable questions such as “How many children do you have?” generally are agreed to have face validity. But it becomes more difficult to assess face validity in regard to more complicated business phenomena. For instance, consider the concept of customer loyalty. Does the statement “I prefer to purchase my groceries at Delavan Fine Foods” appear to capture loyalty? How about “I am very satisfied with my purchases from Delavan Fine Foods”? What about “Delavan Fine Foods offers very good value”? While the first statement appears to capture loyalty, it can be argued the second question is not loyalty but rather satisfaction. What does the third statement reflect? Do we think it looks like a loyalty statement?
  • 7. Content Validity The content validity of a measuring instrument is the extent to which it provides adequate coverage of the investigate questions guiding the study. If the instrument contains a representative sample of the universe of subject matter of the interest, then the content validity is good. To put it differently, content validity is a function of how well the dimensions and elements of a concept have been delineated
  • 8. Continued… Look at the concept of feminism which implies a person's commitment to a set of beliefs creating full equality between men and women in areas of the arts, intellectual pursuits, family, work, politics, and authority relations. Does this definition provide adequate coverage of the different dimensions of the concept? Then we have the following two questions to measure feminism: 1. Should men and women get equal pay for equal work? 2. Should men and women share household tasks? These two questions do not provide coverage to all the dimensions delineated earlier. It definitely falls short of adequate content validity for measuring feminism
  • 9. CriterionRelated Validity Criterion validity uses some standard or criterion to indicate the a construct accurately. The validity of an indicator is verified by comparing it with another measure of the same construct in which research has confidence. There are two subtypes of this kind of validity 1. Concurrent Validity 2. Predictive Validity
  • 10. Concurrent Validity To have concurrent validity, an indicator must be associated with a preexisting indicator that is judged to be valid. For e.g. we create a new test to measure intelligence. For it to be concurrently valid, it should be highly associated with existing IQ tests (assuming the same definition of intelligence is used). It means that most people who score high on the old measure should also score high on the new one, and vice versa. The two measures may not be perfectly associated, but if they measure the same or a similar construct, it is logical for them to yield similar results.
  • 11. Predictive Validity Criterion validity whereby an indicator predicts future events that are logically related to a construct is called a predictive validity. It cannot be used for all measures. The measure and the action predicted must be distinct from but indicate the same construct. Predictive measurement validity should not be confused with prediction in hypothesis testing, where one variable predicts a different variable in future. For e.g. looking at the scholastic assessment tests being given to candidates seeking admission in different subjects. These are supposed to measure the scholastic aptitude of the candidates the ability to perform in institution as well as in the subject. If this test has high predictive validity, then candidates who get high test score will subsequently do well in their subjects. If students with high scores perform the same as students with average or low score, then the test has low predictive validity
  • 12. Construct Validity Construct validity is for measures with multiple indicators. It addresses the question: If the measure is valid, do the various indicators operate in consistent manner? It requires a definition with clearly specified conceptual boundaries. In order to evaluate construct validity, we consider both theory and the measuring instrument being used. There are two subtypes of this kind of validity 1. Convergent Validity 2. Discriminant Validity
  • 13. Convergent Validity Convergent validity means that multiple measures of the same construct hang together or operate in similar ways. For e.g. we construct "education" by asking people how much education they have completed, looking at their institutional records, and asking people to complete a test of school level knowledge. If the measures do not converge (i.e. people who claim to have college degree but have no record of attending college, or those with college degree perform no better than high school dropouts on the test), then our test has weak convergent validity and we should not combine all three indicators into one measure.
  • 14. Discriminant Validity Also called Divergent validity, discriminant validity is the opposite of convergent validity. It means that the indicators of one construct hang together or converge, but also diverge or are negatively associated with opposing constructs. It says that if two constructs A and B are very different, then measures of A and B should not be associated. For example, we have 10 items that measure political conservatism. People answer all 10 in similar ways. But we have also put 5 questions in the same questionnaire that measure political liberalism. Our measure of conservatism has discriminant validity if the 10 conservatism items hang together and are negatively associated with 5 liberalism ones.
  • 15. Reliability The reliability of a measure indicates the extent to which it is without bias (error free) and hence ensures consistent measurement across time and across the various items in the instrument. In other words, the reliability of a measure is an indication of the stability and consistency with which the instrument measures the concept and helps to assess the “goodness” of measure
  • 16. Stability The ability of the measure to remain the same over time despite uncontrollable testing conditions or the state of the respondents themselves is indicative of its stability and low vulnerability to changes in the situation. This attests to its "goodness" because the concept is stably measured, no matter when it is done. Two tests of stability are testretest reliability and parallelform reliability
  • 17. Test-Retest Reliability Testretest method of determining reliability involves administering the same scale to the same respondents at two separate times to test for stability. If the measure is stable over time, the test, administered under the same conditions each time, should obtain similar results. For example, suppose a researcher measures job satisfaction and finds that 64 percent of the population is satisfied with their jobs. If the study is repeated a few weeks later under similar conditions, and the researcher again finds that 64 percent of the population is satisfied with their jobs, it appears that the measure has repeatability. The high stability correlation or consistency between the two measures at time 1 and at time 2 indicates high degree of reliability. This was at the aggregate level; the same exercise can be applied at the individual level. When the measuring instrument produces unpredictable results from one testing to the next, the results are said to be unreliable because of error in measurement.
  • 18. ParallelForm Reliability When responses on two comparable sets of measures tapping the same construct are highly correlated, we have parallelform reliability. It is also called equivalentform reliability. Both forms have similar items and same response format, the only changes being the wording and the order or sequence of the questions. What we try to establish here is the error variability resulting from wording and ordering of the questions. If two such comparable forms are highly correlated, we may be fairly certain that the measures are reasonably reliable, with minimal error variance caused by wording, ordering, or other factors.
  • 19. Internal Consistency of Measure Internal consistency of measures is indicative of the homogeneity of the items in the measure that tap the construct. In other words, the items should `hang together as a set' and be capable of independently measuring the same concept so that the respondents attach the same overall meaning to each of the items. This can be seen by examining if the items and the subsets of items in the measuring instrument are highly correlated. Consistency can be examined through the interitem consistency reliability and splithalf reliability.
  • 20. Inter-item Consistency reliability This is a test of consistency of respondent’s answers to all the items in a measure. To the degree that items are independent measures of the same concept, they will be correlated with one another
  • 21. Split-Half Reliability It reflects the correlation between two halves of an instrument. The estimates could vary depending on how the items in the measure are split into two halves. The technique of splitting halves in the most basic method for checking internal consistency when measures contain a large number of items. In the split-half method the researcher may take the results obtained from one half of the scale items(e.g. odd-numbered items) and check them against the results from the other half of the items (e.g. even numbered items). The high correlation tells us there is similarity (or homogeneity) among its items.
  • 22. Reliability vs Validity Reliability is a necessary but not sufficient condition for validity. A reliable scale may not be valid. For example, a purchase intention measurement technique may consistently indicate that 20 percent of those sampled are willing to purchase a new product. Whether the measure is valid depends on whether 20 percent of the population indeed purchases the product. A reliable but invalid instrument will yield consistently inaccurate results

Notes de l'éditeur

  1. E.g. Consider the controversy about highway patrol officers using radar guns to clock speeders. A driver is clocked at 83 mph in a 55 mph zone, but the same radar gun aimed at a house registers 28 mph. The error occurred because the radar gun had picked up impulses from the electrical system of the squad car’s idling engine.