The document discusses the concepts of validity and reliability in testing. Validity refers to how well a test measures what it intends to measure, while reliability concerns consistency of measurement. Several types of validity are described, including face validity, construct validity, content validity, and criterion validity. Reliability can be estimated through test-retest methods or assessing internal consistency. Threats to validity such as history effects, maturation, testing, instrumentation and mortality are also outlined. Both validity and reliability are important indicators of quality and are interrelated concepts in evaluating psychological and educational tests.

1. Validity and Reliability
Neither Valid
nor Reliable
Reliable
but not
Valid
Valid &
Reliable
Fairly Valid but
not very
Reliable
Think in terms of ‘the
purpose of tests’ and
the ‘consistency’ with
which the purpose is
fulfilled/met

2. Validity
 Depends on the PURPOSE
 E.g. a ruler may be a valid measuring device
for length, but isn’t very valid for measuring
volume
 Measuring what ‘it’ is supposed to
 Matter of degree (how valid?)
 Specific to a particular purpose!
 Must be inferred from evidence; cannot be
directly measured
 Learning outcomes
1.Content coverage (relevance?)
2.Level & type of student engagement (cognitive,
affective, psychomotor) – appropriate?

3. Reliability
 Consistency in the type of result a test
yields
– Time & space
– participants
 Not perfectly similar result but ‘very close-
to’ being similar
 When someone says you are a ‘reliable’
person, what do they really mean?
 Are you a reliable person? 

4. What do you think…?
 Forced-choice assessment forms are high in reliability,
but weak in validity (true/false)
 Performance-based assessment forms are high in both
validity and reliability (true/false)
 A test item is said to be unreliable when most students
answered the item wrongly (true/false)
 When a test contains items that do not represent the
content covered during instruction, it is known as an
unreliable test (true/false)
 Test items that do not successfully measure the intended
learning outcomes (objectives) are invalid items
(true/false)
 Assessment that does not represent student learning
well enough are definitely invalid and unreliable
(true/false)
 A valid test can sometimes be unreliable (true/false)
– If a test is valid, it is reliable! (by-product)

5. Indicators of quality
 Validity
 Reliability
 Utility
 Fairness
Question: how are they all inter-related?

6. Two methods of estimating
reliability
 Test/Retest
Test/retest is the more conservative method to estimate
reliability. Simply put, the idea behind test/retest is that
you should get the same score on test 1 as you do on
test 2. The three main components to this method are as
follows:
1.) implement your measurement instrument at two
separate times for each subject;
2). compute the correlation between the two separate
measurements; and
3) assume there is no change in the underlying condition
(or trait you are trying to measure) between test 1 and
test 2.

7.  Internal Consistency
Internal consistency estimates reliability by
grouping questions in a questionnaire that
measure the same concept. For example, you
could write two sets of three questions that
measure the same concept (say class
participation) and after collecting the responses,
run a correlation between those two groups of
three questions to determine if your instrument
is reliably measuring that concept.
Two methods of estimating
reliability

8.  The primary difference between
test/retest and internal consistency
estimates of reliability is that test/retest
involves two administrations of the
measurement instrument, whereas the
internal consistency method involves only
one administration of that instrument.

9. Validity
Cook and Campbell (1979) define it as the "best available
approximation to the truth or falsity of a given inference,
proposition or conclusion.“
In short, were we right?
Let's look at a simple example. Say we are studying the
effect of strict attendance policies on class participation.
We see that class participation did increase after the
policy was established. Each type of validity would
highlight a different aspect of the relationship between
our treatment (strict attendance policy) and our
observed outcome (increased class participation).

10. Types of Validity
1. Conclusion validity
2. Internal Validity
3. Construct validity
4. External validity

11. Conclusion validity
asks is there a relationship between the
program and the observed outcome? Or,
in our example, is there a connection
between the attendance policy and the
increased participation we saw?

12. Internal Validity
asks if there is a relationship between the
program and the outcome we saw, is it a
causal relationship? For example, did the
attendance policy cause class participation
to increase?

13. Threats To Internal Validity
There are three main types of threats to internal validity –
single group
multiple group
social interaction threats.
Single Group Threats apply when you are studying a
single group receiving a program or treatment. Thus, all
of these threats can be greatly reduced by adding a
control group that is comparable to your program group
to your study.

14. History Threat occurs when an historical event
affects your program group such that it causes
the outcome you observe (rather than your
treatment being the cause). In our earlier
example, this would mean that the stricter
attendance policy did not cause an increase in
class participation, but rather, the expulsion of
several students due to low participation from
school impacted your program group such that
they increased their participation as a result.
Threats To Internal Validity-
Single Group

15. Threats To Internal Validity-
Single Group
 A Maturation Threat to internal validity occurs
when standard events over the course of time
cause your outcome. For example, if by chance,
the students who participated in your study on
class participation all "grew up" naturally and
realized that class participation increased their
learning (how likely is that?) - that could be the
cause of your increased participation, not the
stricter attendance policy.

16. Threats To Internal Validity-
Single Group
 A Testing Threat to internal validity is simply
when the act of taking a pre-test affects how
that group does on the post-test. For example, if
in your study of class participation, you
measured class participation prior to
implementing your new attendance policy, and
students became forewarned that there was
about to be an emphasis on participation, they
may increase it simply as a result of involvement
in the pretest measure - and thus, your outcome
could be a result of a testing threat - not your
treatment.

17. Threats To Internal Validity-
Single Group
 An Instrumentation Threat to internal
validity could occur if the effect of
increased participation could be due to the
way in which that pretest was
implemented.

18. Threats To Internal Validity-
Single Group
 A Mortality Threat to internal validity occurs
when subjects drop out of your study, and this
leads to an inflated measure of your effect. For
example, if as a result of a stricter attendance
policy, most students drop out of a class, leaving
only those more serious students in the class
(those who would participate at a high level
naturally) - this could mean your effect is
overestimated and suffering from a mortality
threat.

19. Multiple Group Threats
involve the comparability of the two groups in your study, and whether or not
any other factor other than your treatment causes the outcome. They also
mirror the single group threats to internal validity.
 A Selection-History threat occurs when an event occurring between the
pre and post test affects the two groups differently.
 A Selection-Maturation threat occurs when there are different
rates of growth between the two groups between the pre and post
test.
 Selection-Testing threat is the result of the different effect from
taking tests between the two groups.
 A Selection-Instrumentation threat occurs when the test
implementation affects the groups differently between the pre and
post test.
 A Selection-Mortality Threat occurs when there are different rates
of dropout between the groups which leads to you detecting an
effect that may not actually occur.
 Finally, a Selection-Regression threat occurs when the two groups
regress towards the mean at different rates.

20. Construct validity
Asks if there is there a relationship between
how I operationalized my concepts in this
study to the actual causal relationship I'm
trying to study
In our example, did our treatment
(attendance policy) reflect the construct of
attendance, and did our measured
outcome - increased class participation -
reflect the construct of participation?

21. External validity
Refers to our ability to generalize the results
of our study to other settings.
In our example, could we generalize our
results to other classrooms? Other
schools?

22. Types of validity measures
 Face validity
 Construct validity
 Content validity
 Criterion validity
1. Predictive
2. Concurrent

23. Face Validity
 Does it appear to measure what it is supposed to
measure?
 Example: Let’s say you are interested in measuring,
‘Propensity towards violence and aggression’. By
simply looking at the following items, state which
ones qualify to measure the variable of interest:
– Have you been arrested?
– Have you been involved in physical fighting?
– Do you get angry easily?
– Do you sleep with your socks on?
– Is it hard to control your anger?
– Do you enjoy playing sports?

24. Construct Validity
 Does the test measure the ‘human’
CHARACTERISTIC(s) it is supposed to?
 Examples of constructs or ‘human’
characteristics:
– Mathematical reasoning
– Verbal reasoning
– Musical ability
– Spatial ability
– Mechanical aptitude
– Motivation

25. Content Validity
 Does the DV measure the empirical,
operationalized variable being studied?
 Does the exam cover adequately cover the
range of material?

26. Criterion Validity
 The degree to which content on a test
(predictor) correlates with performance on
relevant criterion measures (concrete criterion
in the "real" world?)
 If they do correlate highly, it means that the test
(predictor) is a valid one!
 E.g. if you taught skills relating to ‘public
speaking’ and had students do a test on it, the
test can be validated by looking at how it relates
to actual performance (public speaking) of
students inside or outside of the classroom

27. Two Types of Criterion Validity
 Concurrent Criterion Validity = how well
performance on a test estimates current
performance on some valued measure (criterion)?
(e.g. test of dictionary skills can estimate students’
current skills in the actual use of dictionary –
observation)
 Predictive Criterion Validity = how well
performance on a test predicts future performance
on some valued measure (criterion)? (e.g. reading
readiness test might be used to predict students’
achievement in reading)

28. Reliability
 Measure of consistency of test results
from one administration of the test to the
next
 Generalizability – consistency (interwoven
concepts) – if a test item is reliable, it can
be correlated with other items to
collectively measure a construct or content
mastery

29. Measuring Reliability
 Test – retest
Give the same test twice to the same group with
any time interval between tests
 Equivalent forms (similar in content, difficulty level, arrangement, type
of assessment, etc.)
Give two forms of the test to the same group in
close succession
 Split-half
Test has two equivalent halves. Give test once,
score two equivalent halves (odd items vs. even
items)
 Cronbach Alpha (SPSS)
Inter-item consistency – one test – one
administration
 Inter-rater Consistency (subjective
scoring)