W4 Readings Flashcards
Validity and reliability of measurement instruments used in researched
Kimberlite article
Reliability
The obtained and observed score through a measuring Instrument is composed of both the true score which is unknown and error in the measurement process
True score
The score that a person would have received if the measurement were perfectly accurate
Pre-testing or pilot testing
An instrument allows for the identification of such scores refinement of the instrument than focusses on minimizing measurement error
Reliability estimates are used to evaluate
1
1.The stability of measures administered at different times to the same individual
2The equivalent of sets of items from the same test (internal consistency) Or of different observers scoring a behaviour or event using the same Instrument (Interrater reliability)
Reliability coefficient range from…..
0-1
Higher coefficient means higher levels of reliability
Stability
Is determined by administering the test at two different points in time to the same individual and determining the correlation or strength of Association of the two sets of scores
Internal consistency
Gives an estimate of the equivalent of sets of items from the same test
Ex,A set of questions aimed at assessing quality of life or disease severity
The coefficient of internal consistency provides an estimate of the reliability of measurement and is based on the assumption that items measuring the same contract should correlate
What is the widely used method for estimating internal consistency reliability
Cronbatch alpha
What is cronbatch’s alpha¿
What is it used for?
What makes cronbatch Alpha high? Major gains?
A function of the average intercorrelations of items and the number of items in the scale
Used for summmated scales such as quality of life Instruments
All things being equal, the greater the number of items in the summated scale
Additional items up to approximately 10, when the increase in reliability for each additional item levels off. This is one reason why the use of a single item to measure a construct is not optimal
Having multiple items to measure a construct aids in the determination of the reliability of measurement and in general improves the reliability or precision of the measurement
Interrater reliability /Intero observer agreement
Establishes the equivalent of readings obtained with an instrument when used by different observers
If a measurement process involves judgements or ratings by observers, a reliable measurement will require consistency between different raters
Requires completely independent ratings of the same event by more than one rater
No discussion or collaboration can occur when reliability is being tested
Reliability is determined by the correlation of the scores from two or more independent raters Or the coefficient of agreement of the judgements of the Raters 
For categorical variables, _______ _____ is commonly used to determine the coefficient of agreement.
______ Is used when two raters or observes Classify events or observations into categories based on rating criteria

For categorical variables, Cohens Kappa is commonly used to determine the coefficient of agreement.
Kappa Is used when two raters or observes Classify events or observations into categories based on rating criteria
Rather than a simple percent agreement, KAPPA takes into account the agreement that could be excepted by chance alone
Interrater reliability should be establish when datas are abstracted from medical charts or when diagnosis or assessments are made for research purposes
It also depends on…
Developing precise operational definitions of variables being measured as well as having observers well trained to use the instrument
it is optimized when criteria are explicit and raters are trained to apply the criteria
Raters must be trained how to make a decision
I that and event has occurred or how to determine which point on the scale measuring strength or degree a phenomenon should be applied.
The more that individual judgement is involved in the reading, the more crucial it is the independent observers agreed when applying the scoring criteria.
Training should include multiple cases such as
They respond to simulated situation they will encounter and rate, interrater reliability is calculated disagreements or clarified and a criterion level of agreement is Met
Interrater reliability you should be verified
Throughout the study even when established observational instruments are being used or criteria or explicit research That relies on observations or judgements should check reliability and the study protocol should include procedures to determine the level of observer agreement
I percentage of observation such as number of charts reviewed his randomly selected for scoring by two independent readers rather than requiring that to raiders judge all observation
Data to establish the consistency…
With which the primary rater applies the criteria overtime are important for establishing the reliability of an instrument
Rater drift can occur when 
An individual rater alters the way he or she applies the scoring criteria such as becoming more lenient or stringent over time 
Investigators who build and reliability checks throughout the study is data or collected rather than waiting until the end of data collection can identify instances where into regular reliability has become to deteriorate perhaps to the 
Rater drift