Transcript Beck Depression Inventory II (BDI-II)

Measurement Concepts &
Interpretation
Scores on tests can be interpreted:
• By comparing a client to a peer in the norm
group to determine how different the client is
from the norm group (inter-individual)
– Scores provided in norm tables
– The score in the norm table usually indicates how the
client with peers in same age group or grade
Interpretation, cont.
• Comparing a client
with his or her own
performance (intraindividual)
Define:
• Mean
• Median
• Mode
So you wanna use psychological tests…
• Um, CAREFULLY review the test manual
• Consider these aspects:
– Theoretical Orientation of test/instrument
– Practical Considerations
– Standardization
– Reliability
– Validity
Gary Groth-Marnat, 2003
Theoretical Orientation
• Do you adequately understand the
theoretical construct the test is supposed
to be measuring?
– If not, do some research.
• Do the test items correspond to the
theoretical description of the construct?
– Usually manuals provide individual analyses of
the items…are the items relevant?
Practical Considerations
• If reading is required by the examinee, does his or
her ability match the level required by the test?
– Tests vary in terms of the level of education
• How appropriate is the length of the test?
– Some are too damn long and who likes that?
• You can always get additional training for some
tests so you become Über good at it.
Standardization (adequacy of norms)
• Is the population to be test similar to the
population the test was standardized on?
• Was the size of the standardization sample
adequate?
• Have specialized subgroup norms been
established?
• How adequately do the instructions permit
standardized administration?
Norms!
Reliability
• The reliability of a test refers to its degree
of stability, consistency, predictability, and
accuracy
• Are reliability estimates sufficiently high?
(correlations generally around .90 for clinical
decision making and around .70 for research
purposes)
• What implications do the relative stability of
the trait, the method of estimating
reliability, and the test format have on
reliability?
You tell me…
• Test-Retest Reliability
– The reliability coefficient is calculated by correlating the
scores obtained by the same person on two different
administrations.
• Alternate Forms
– Trait is measured several times on the same individual
by using parallel/alternate forms of the test – the
different measurements should produce similar results
• Split half Reliability
– Test only given once (items split in half…and two halves
are correlated)
• Interscorer Reliability
– When scoring is based partially on the judgment of the
examiner (e.g., Rorschach). Responses are scored by
two people or two people score one client’s responses)
All tests have a degree of error
• The inevitable, natural variation in human
performance
– Measures of ability usually have less variability
than measures of personality…why?
• Psychological testing methods are
necessarily imprecise
– Constructs in psychology are measured
indirectly
Standard Error of Measurement
• Test scores consist of both truth and error
• SEM provides a range of to indicate how extensive
that error is likely to be
– The higher the reliability, the narrower the range of
error
• The SEM is a standard deviation score.
– A SEM of 3 on an IQ test would indicate that individual’s
score has a 68% chance of being +/-3 IQ points from
the estimated true score – refer back to the normal
distribution curve
– The SEM is a statistical index of how a person’s
repeated scores on a specific test would fall around a
normal distribution (also referred to as a confidence
interval)
Validity
• Wheras reliability addresses issues of consistency,
•
•
validity assess what the test is to be accurate
about.
What criteria and procedures were used to
validate the test?
Will the test produce accurate measurements in
the context and for the purpose for which you
would like to use it?
– A psychological test is not valid in any abstract or
absolute sense. It must be valid in a particular
CONTEXT and for a specific group of people.
Face validity
• Face validity is present if the test looks
good to the persons taking it, the
policymakers who decide to include it in
their programs, and to other untrained
personnel.
Criterion validity
• Concurrent validity
– Measurements taken at the same, or approximately
the same, time as the test
– Concurrent validation is preferable if an assessment of
the client’s current status is required
• Predictive validity
– Outside measurements that were taken some time
after the test scores were derived. For example, the
predictive validity may be evaluated by correlating
test scores with other scores from similar measures a
year after the initial testing
Construct Validity
• The extent to which the test measures a
theoretical construct or trait
– First, the trait must be carefully analyzed
– Consider the ways in which the trait should relate to
other variable
– Test the hypothesized relationships
• Does the test converge with variables that are
•
theoretically similar to it?
Does it discriminate from variables that are
dissimilar to it?
Incremental validity
• For a test to be considered useful and
efficient, it must be able to produce
accurate results above and beyond the
results that could be obtained with greater
ease and less expense
• Hey, self-assessments are pretty handy!
Beck Depression Inventory II (BDI-II)
• Add up the score for each of the twenty-
one questions and obtain the total. The
highest score on each of the twenty-one
questions is three, the highest possible total
for the whole test is sixty-three. The lowest
possible score for the whole test is zero.
Only add one score per question (the
highest rated if more than one is circled).
“So what does my BDI-II score mean?”
• Below 4 = possible denial of depression,
faking good
• 05-09 = these ups and downs are
considered normal (i.e., suck it up)
• 10-18 = mild to moderate depression
• 19-29 = moderate to severe depression
• 30-63 = severe depression
• Over 44 = pretty damn high even for
severely depressed persons;
possible exaggeration of symptoms
Same for BAI
• 0-21 = low anxiety
• 22-35 = moderate anxiety
• Over 36 = high anxiety,
may be severe