4: Validity Reliability Flashcards
(49 cards)
What contributes to soundness of experiments?
precision
accuracy
sensitivity
specificity
reliability
validity
what is precision?
Consistency, reliability, homogeneity of the data
what is accuracy?
Based on the precision of the measurements. Good accuracy if averaged values ≈ standard. Standards are rare in the biological sciences (behavioural or neurosciences). In psychophysics (Signal Detection Theory), accuracy = specificity + sensitivity
what is sensitivity?
Measures should be sensitive enough to detect differences in a characteristic that are important to the investigator
what is specificity?
Measures should be specific to the characteristics, group, phenomenon, etc. investigated
what is reliability?
Consistency of the measures. Precision
what is validity?
Does a variable represent what it is intended?
what are nuisance variables?
We hinted at this before with the concept of “distortion”
Two types:
Systematic error or bias
Random error (or error variance)
what is influenced by Systematic error or bias?
accuracy
what type of variables are a source of bias?
extraneous/ confounded variables
Types of biases/systematic errors and their solutions
Observer/Experimenter»>
Blinding procedures
Subject/Participant»_space;> Blinding/ Unobtrusive measures
Apparatus»_space;> Calibration
what is random error?
The precision of measurements (and therefore the consistency and reliability) is influenced by random error unpredictable fluctuations)
sources of random error
Random error is due to random fluctuations in participants, experimental conditions, methods of measurement, etc.
Main sources of random error:
*Observer / experimenter reliability
*Participant / subject reliability
*Instrument / apparatus reliability
contributors of precision
Calibration of an apparatus
Consistency of a participant
Environmental and other factors
Archery example: Bow/sight, archer, wind
How to assess precision?
Measures of variability (descriptive statistics)
measures of concordance
what are measures of variability
Standard deviation (sd) of repeated measurements.
Coefficient of variation (cv): (sd ÷ mean) × 100
what are measures of concordance?
Correlation coefficient: Consistency of results of paired
measurements. The coefficient of correlation is an index of
concordance
what is reliability?
Consistent results over repeated measurements. Reliability refers to the PRECISION of your measures
assessment methods
Test-retest reliability/consistency: Stability of test scores over time.
Alternative (parallel) forms reliability/consistency: e.g., recognition/recall example with
tests.
Internal consistency: How consistent is the measure across items intended to measure the same concept, e.g., split-half reliability/consistency » use of two lists in a memory test.
Inter-rater reliability: see next slide.
In some cases: Intra-rater reliability
what is Inter-observer/rater consistency or reliability?
consistency of recording
and scoring between ALL OBSERVERS
with an inter- observer reliability measure such as an index of concordance, kappa coefficient, Kendall coefficient
what is Intra-observer/rater consistency or reliability?
each observer, individually, records,
interprets or identifies SIMILAR behaviours or events the SAME
WAY.
with an intra- observer reliability measure)
what does intra mean
within
what does inter mean
between
what is validity about?
Validity is about the threats to valid inference making; Is the procedure you chose measures what it is intended to measure?