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Reliability and Validity

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Reliability and Validity Reliability When a Measurement Procedure yields consistent scores when the phenomenon being measured is not changing. – PowerPoint PPT presentation

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Title: Reliability and Validity


1
Reliability and Validity
2
Reliability
  • When a Measurement Procedure yields consistent
    scores when the phenomenon being measured is not
    changing.
  • Degree to which scores are free of measurement
    error
  • Consistency of measurement

3
VALIDITY
  • The extent to which measures indicate what they
    are intended to measure.
  • The match between the conceptual definition and
    the operational definition.

4
RELATIONSHIP BETWEEN RELIABILITY AND VALIDITY
  • Necessary but not sufficient
  • Reliability is a prerequisite for measurement
    validity
  • One needs reliability, but its not enough

5
Example
  • Measuring height with reliable bathroom scale
  • Measuring aggression with observer agreement by
    observing a kid hitting a Bobo doll

6
Types of Reliability Measurement
  • 1. Stability Reliability
  • 2. Equivalence Reliability

7
Stability Reliability
  • Test-retest
  • SAME TEST DIFFERENT TIMES
  • Testing phenomenon at two different times
  • The degree to which the two measurements of Sam
    Ting, using same measure, are related to one
    another
  • Only works if phenomenon is unchanging

8
Example of Stability
  • Administering same questionnaire at 2 different
    times
  • Re-examining client before deciding on
    intervention strategy.
  • Running trial twice (e.. g. errors in tennis
    serving)

9
Notes on Stability Reliability
  • When ratings are by an observer rather than the
    subjects themselves, this is called Intraobserver
    Reliability or Intrarater Reliability.
  • Answers about the past are less reliable when
    they are very specific, because the questions may
    exceed the subjects capacity to remember
    accurately.

10
Equivalence Reliability
  • Inter-item (split ½)
  • Parallel forms Different types of measures
  • Interobserver Agreement
  • -Is every observer scoring the same ?

11
1. Inter-item Reliability
  • (Internal consistency) The association of
    answers to a set of questions designed to measure
    the same concept.

12
Note on Inter-item Validity
  • The stronger the association among individual
    items and the more items included, the higher the
    reliability of an index
  • Cronbachs alpha is a statistic commonly used to
    measure inter-item reliability
  • Cronbachs alpha is based on the average of all
    the possible correlations of all the split 1/2s
    of a set of questions on a questionnaire

13
2. Parallel forms of Reliability
  • Split ½ (inter-item)
  • Different types of measures
  • Interobserver Reliability
  • Is everyone measuring the same thing ?
  • Different measures same time

14
3.Interobserver Reliability
  • Correspondence between measures made by different
    observers.

15
Note for Stat Students Only
  • The text inadvertently describes a 3rd type of
    reliability that were not concerned with in this
    class goodness of fit about a slope line.
    Its sometimes referred to as random measurement
    error.
  • Save this for Grad School )

16
Note on Reliability
  • For Statistics people, the following quote refers
    to goodness of fit around a slope line due to
    measurement error.
  • Secondary Definition of Reliability from a
    previous slide
  • or that the measured scores changes in direct
    correspondence to actual changes in the
    phenomenon

17
  • And Now Onto Validity..

18
Types of Validity
  • 1. Content Validity
  • Face Validity
  • Sampling Validity (content validity)
  • 2. Empirical Validity
  • Concurrent Validity
  • Predictive Validity
  • 3. Construct Validity

19
Face Validity
  • confidence gained from careful inspection of a
    concept to see if its appropriate on its face
  • In our collective intersubjective, informed
    judgment, have we measured what we want to
    measure?
  • (N.B. use of good judgment)

20
Example of Face Validity
  • Rosenbergs self esteem scale questions

21
Content validity
  • Also called sampling validity
  • establishes that the measure covers the full
    range of the concepts meaning, i.e., covers all
    dimensions of a concept
  • N.B depends on good judgment

22
Example of content validity
  • Earlier SES scale in class
  • Authoritarian personality questions from Walizer
    Wienir

23
Note
  • Actually I think face and content validity are
    probably Sam Ting

24
EMPIRICAL Validity
  • Establishes that the results from one measure
    match those obtained with a more direct or
    already validated measure of the same phenomenon
    (the criterion)
  • Includes
  • Concurrent
  • Predictive

25
Concurrent Validity
  • Validity exists when a measure yields scores that
    are closely related to scores on a criterion
    measured at the same time
  • Does the new instrument correlate highly with an
    old measure of the same concept that we assume
    (judge) to be valid? (use of good judgment)

26
Example of concurrent validity
  • Aronsons doodle measure of achievement
    motivation.
  • Act vs. SAT

27
Predictive Validity
  • Exits when a measure is validated by predicting
    scores on a criterion measured in the future
  • Are future events which we judge to be a result
    of the concept were measuring anticipated
    predicted by the scores were attempting to
    validate
  • Use of good judgment

28
Examples of Predictive Validity
  • Bronson screening test for at risk parenting
    followed up by interviewing and observing family
    members and school staff later
  • Sat / ACT scores and later college performance
    (grades)
  • Grades are judged to be measured validly

29
Whats a Construct? NSB
  • Multidimensional concept
  • SES
  • Industrialization
  • Fuzzy concept / hard to define
  • Ego strength
  • Love
  • Concept build out of other concepts
  • Forcemass acceleration
  • Ya better know these!!!!!

30
Consider This
  • If a construct is hard to conceptualize doesnt
    it make sense that itll be more difficult to
    operationalize and validate?

31
Construct validity
  • established by showing that a measure is (1)
    related to a variety of other measures as
    specified in a theory, used when no clear
    criterion exists for validation purposes (2)
    that the operationalization has a set of
    interrelated items and (3) that the
    operationalization has not included separate
    concepts

32
Construct validity
  • Check the intercorrelation of items used to
    measure construct judged to be valid
  • Use theory to predict a relationship and use a
    judged to be valid measure of the other variable
    then check for relationship
  • Demonstrate that your measure isnt related to
    judged to be valid measures of unrelated concepts

33
Convergent Validity
  • Convergent validity achieved when one measure
    of a concept is associated with different types
    of measures in the same concept (this relies on
    the same type of logic as measurement
    triangulation)
  • Measures intercorrelated

34
Example of questions that Interrelate
  • Questions for Companionateintimacy
  • We get along well
  • We communicate
  • We like the same stuff
  • Our chemistry is good
  • We support each other

35
Discriminant Validity
  • Discriminant validity scores on the measure to
    be validated are compared to scores on measures
    of different but related concepts and
    discriminant validity is achieved if the measure
    to be validated is NOT strongly associated with
    the measures of different concepts
  • Measure not related to unrelated concepts

36
Questions for Passion
  • I think my partner is HOT
  • My partner turns me on
  • When Im with my partner I just feel the
    electricity

37
Using theory
  • Measure of constructs predicts what theory says
    it should

38
  • Companionate rel longevity
  • satisfaction
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