Measurement Tools Flashcards
What are the types of measurement tools?
descriptive discriminative, predictive, evaluative and diagnostic
What do descriptive measurement tools do?
describes the event/functional status
What do discriminative measurement tools do?
discriminate between different concepts or qualities that we want to assess. Compare against normative data.
What do predictive measurement tools do?
predict future events (may also discriminate between events). Can classify people into predetermined categories or can predict future abilities and outcomes
What do diagnostic measurement tools do?
diagnose a health condition
What do evaluative measurement tools do?
evaluate health outcomes, detect change over time. In order to do this they must be sensitive to change and should have a good test-retest reliability
What is the purpose of measurement?
to give an operational/practical definition of the construct of the question/purpose
What is the difference between 2 measurements called?
variation in the measurements/error
When is error present?
always
What influences error?
client’s attributes, evaluation/instrument, therapist/rater and environment
What is the sum of measurement error?
observed score = true ability + random error +/- systematic error
What is systematic error?
bias
What is random error?
variability
What is a reliable tool?
One that produces consistent results over repeated trials
What can effect the stability of a tool?
translation of instruments - may not be culturally appropriate between different populations
When would you use a measurement tool?
- to gather info
- to diagnose
- provide prognostic info
- provide initial baseline assessment of functional status
- progress or outcome of therapy
What is a standardized assessment?
a published test that has uniformity in administering and scoring it. Detailed instructions included which allows you to collect quantifiable data. Describes the psychometric properties of the tool.
What is standardization?
process of taking an assessment and developing a fixed protocol for administering and scoring and completing studies on the psychometric properties of the tool.
What is norm-referenced?
scores are obtained from a representative group of people (norms) which informs of average performance as well as range above and below this.
What is important when looking at norm-referenced tests?
must be up to date ad reflect the attributes of the population.
What is a criteria?
an established principle/standard based on a known standard.
What properties should measurements have?
reliability, validity and responsiveness to change
What are the characteristics of a good measurement?
- concept being measures is well defined and measured accurately
- everyone gets the same answer using the same info
- everyone gets a different answer when data changes
- everyone knows what the results mean
- error is reduced as much as possible
- measurement strategy can easily be used
What are some aspects of clinical utility?
- cost
- time
- training
- energy and effort
- portability
- acceptability
What costs must be considered?
- initial outlay: manual, forms, test materials etc.
- recurring costs: forms
- equipment not included in the test
- cost of specific training or expertise
What aspects of time should be considered?
- time to administer: poor stamina/attention span = unreliable results
- prepare environment
- learn test administration
- analyse and interpret test results
- report writing
What must considered for the test to have a good energy and effort level?
- therapist learning to administer the test
- mobility and transfers
- demands on the assessor and test-taker
What aspects of portability must be considered?
- heaviness/bulkiness
- Is it easily transportable
- can it be used in small places?
- multiple parts to the assessment needing to be transported
- purchase equipment to carry it?
What must be considered in order for the test to be acceptable?
- match of assessment with philosophy and frameworks used in practice context
- will the client find this useful?
- will it cause stress and anxiety?
- does the assessment look professional?
What is responsiveness?
ability to detect change
How can responsiveness be quantified?
- indicators of effect size
- a modified effect size statistic proposed by Guyatt
- receiver operating characteristic (ROC) curves
How is effect size measures?
cohen’s-d
What is a small effect size?
0.2 or less
What is a moderate effect size?
0.8 or more
What scores of effect size indicate responsiveness to clinical change.
The higher the score, the more responsive it is
How is effect size calculated?
the differences in means between measurement points (baseline and follow up) divided by measure of variance (standard deviation of baseline)
What is Guyatt’s responsiveness coefficient (RC)
the smallest difference in a measure that signifies a clinically significant change
What is the ROC curve?
reciever operating characteristic curve. True positive rate (sensitivity) is plotted in function of the false positive rate (100-specificity) for different cut-off points
What does each point on the ROC curve indicate?
sensitivity/specificity pair corresponding to a particular decision threshold
What is specificity?
Probability that a test result will be negative when disease or change isn’t present
What does the ROC curve look like for a test with perfect discrimination?
curve passes through upper left corner (100% in both axes)
