Research Objectives 2 & QUEST Flashcards
Can theoretically have any value along a continuum within a defined range
Ex: wt in lbs
Continuous variables
Can only be described in whole integer unit
Ex: HR in BPM
Discrete variables
Can only take on two values
Ex: yes or no one a survey
Dichotomous variable
What is the challenge of measuring constructs?
It subjective, used with abstract variables and measured according to the expectations of how a person who possesses a specified trait would behave, look, or feel in certain situations.
category/classifications (Ex: blood type, gender, dx)
Nominal
numbers in rank order, inconsistent/unknown intervals. Based on greater than, less than (Ex: MMT, function, pain)
Ordinal
numbers have rank orders and equal intervals, but no true zero. Can be added or subtracted, cannot be used to interpret actual quantities (Ex: Fahrenheit vs celsius, shoe size)
Interval
numbers represent units w/ equal intervals measured from true zero (Ex: Height, wt, age)
Ratio
What is the relevance of identifying measurement scales for statistical analysis?
mathematical operations
Meaningful interpretations
Statistical procedure requiring applied mathematical manipulations, requiring interval or ratio data… Mean, median, mode
Parametric tests
Statistical procedure that does not make the same assumptions and are designed to be used w/ ordinal and nominal data
Non parametric tests
Two important forms of reliability in clinical measurement
Relative and absolute reliability
Reflects true variance as a proportion of total variance in a set of scores.
Intraclass correlation coefficients (ICC) and kappa coefficients are commonly used
Relative reliability
Indicates how much of a measured value, expressed in the original units, is likely due to error
Most commonly uses standard error of measurement
Absolute reliability
any observed score involves true score (fixed value) and unknown error component (small or large)
Classical measurement theory
true score ± error component equals…..
Observed score
matter of chance, possibly arising from factors such as examiner or subject inattention, instrument imprecision, or unanticipated environmental fluctuation.
Can occur through the measuring instrument itself for example: Imprecise instruments or environmental changes affecting instrument performance can also contribute to random error
Random errors
predictable errors of measurement. They occur in one direction, constantly overestimating or underestimating the true score.
Consistent & are not a threat to reliability. Instead, it only threatens the validity of a measure.
Systematic errors
typical sources of measurement error
The person taking the measurements — the raters
The measuring instrument
Variability/consistency in the characteristic being measured
What is the effect of regression toward the mean in repeated measurement?
can interfere when researchers try to extrapolate results observed in a small sample to a larger population of interest.
statistical phenomena when extreme scores are used in the calculation of measured change. Extreme scores on an initial test are expected to move closer (or regress) toward the group average (mean) on a second test.
Regression towards the mean (RTM)
Discuss how concepts of agreement and correlation relate to reliability
Through interrater agreement and correlation, a study is likely to be more reliable
determines the ability of an instrument to measure subject performance consistently
Test-retest
time intervals between tests must be considered
Test-retest intervals
carryover influenced by practice or learning during the initial trial alters performance on subsequent trials
Carryover
when the test itself is responsible for observed changes in a measured variable
Testing effects