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Consists of rules for assignment number
of objects to represent quantities of attributes
Process of assigning numbers to variables
advantages to measurement x4
removes guess work from gathering info, can be independently verified by others (objectivity), produce precise info, language of communication
these are problematic because they represent an unknown quantity and they are variable
errors of measurement
what contributes to errors of measurement
situational contaminants, transitory personal factors, response-set biases, Instrument format, Administration variations, Instrument clarity, Item sampling-errors
number of relatively enduring
characteristics of the respondents that can interfere
with accurate measures of the target attribute.
alterations in the methods of collecting data from one subject to the next
if directions for obtaining measures are vague or poorly
understood, then scores may be affected
sometimes introduced as a result of the sampling of items used to measure an attribute
technical characteristics of an instrument can influence the obtained measurement
Instrument format (example: open ended questions vs closed ended questions)
The degree of consistency with which an instrument measures the attribute it is
supposed to be measuring
administration of the same
test to a sample of individuals on two occasions
then compare the scores obtained
• Compute a reliability coefficient
advantages of reliability x 3
- Test-retest method is easy
- Can be used with self- report, observational & physiologic
- Used with traits that are relatively enduring such as personality,
abilities or physical attributes such as height
disadvantages of reliability
- Many traits do change over time- regardless of the measure eg
(behaviors, attitudes etc)
- Second administration may be influenced by memory of first
- Subjects may change as a result of taking the test the first time
- Responses could be haphazard if subject is bored or impatient
correlation of various items
within the instrument (homogeneity), measures the
same characteristic, Most widely used method for reliability, Requires only one test administration
- The items composing a test are split into two groups and scored independently
- Score on the two half-tests are used to compute a correlation coefficient
disadvantages of split-half technique
Reliability estimates can be obtained by using different splits (odd/even; first/second half)
Produce a reliability coefficient that can be interpreted as the other correlation coefficients, Yields values of 0 to 1.0
Chronbach's alpha or Kuder-Richardson
20 (KR 20)
why is Chronbach's alpha or Kuder-Richardson better than split-half technique
because it computes all possible splits to estimate homogeneity
Comparing two versions of same instrument or two observers (inter-rater reliability) measuring the same event
what is the goal of equivalence
Goal is to determine the consistency or equivalence of the instruments in yielding
measurements of the same traits in the same people
is estimated by having two
or more trained observers watching some event
simultaneously & independently recording the
relevant variables according to a predetermined
plan or coding system
how are the results of the Interrater reliability used?
Results are used to compute an index of equivalence or agreement. Can use a correlation coefficient to compare results
* Refers to the degree to which an instrument measures what it is supposed to be measuring.
(Accuracy of the measure)
o Whether the instrument looks as though it is measuring the appropriate critical variable (or construct).
o Not the strongest way to determine validity
o How well the instrument represents the characteristic to be assessed
o Used for affective measures (feeling, emotions, psychological traits) & cognitive measures (knowledge)
o Based on judgment of experts
o Must ask the question: "how representative are the questions on this test of the universe of all questions that might be asked on this topic?"
* Cognitive Scale
Emphasis is on establishing the relationship between the instrument and some other criteria, Criterion must be clear cut & objective
Criterion-Related validity examples
* For example: instrument to measure birth control use among sexually active teenage girls-criterion to compare it to may be subsequent premarital pregnancy
* Measure professionalism among nurses (attribute to be measured) to number of articles published (criterion)
* Measure effectiveness of nursing care to supervisory ratings of nurse
true or false: Criterion related validity is a relationship but also is a predictive relationship
o Judgment is to the degree to which an instrument can accurately identify a difference in the present
o Use 2 instruments to measure the same concept
Method for indentifying clusters of related variables.
Procedure is used to identify and group together different measures of some underlying attribute
* Factor Analysis
each cluster is called a factor, what does this represent
* Represents a group of items that identify the same characteristic
Beliefs that are held to be true but have not necessarily been proven OR A principle that is accepted as being true based on logic or reason, without proof
beliefs assumed to be true by a large percentage of society (all humans need love)
characteristics of assumptions
Derived from a theory of previous research (stress causes disease).
Specific to a certain research study (evidence of a fit between what the researcher believes can happen & the data produced)
Uncontrolled variables that may affect study results and limit the generalizability of the findings
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