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Class 9 Dependent Variables, Instructions/Literature Review. Chapters 13, 22 Corkin , & P&B 7 – SP 13. Dependent Variables: Continuous. Psychometric Properties Validity Reliability. Validity. Convergent and Discriminate Validity Correlation Predictive Validity - PowerPoint PPT Presentation
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Validity
Convergent and Discriminate Validity◦Correlation
Predictive Validity◦Correlation- Differences across groups◦Longitudinal
Construct Validity◦ Factor structure-latent constructs
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ReliabilityThe extent to which scores show true variance in attributes across participants as opposed to error variance ◦ Assumption: Error variance is random,
therefore it does not correlate with anything
◦ More items of good quality = higher reliability
◦ One item scales have very low reliability; around r =.25
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Types of Measures
Observational Measures
Self-Report Paper-and-Pencil Measures◦Content tests- right/wrong answers
◦Likert-scales
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Sources of Measurement Error Specific error
◦ something unique about the instrument/observational task that differs from what the researcher intended (e.g. social desirability; reading level; idioms)
Transient error◦ some temporary factor that affects
the measurement (e.g. order of instruments; historical events; noise while observations occur; tiredness)
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Sources of Measurement Error
Scoring/Recording error◦ Tend to be random (self-report/raters)
Inter-rater disagreement/observer drift ◦ in observation studies, what initially
may appear as antisocial behavior may later be judged more normative
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Types of Reliability Inter-Scorer Test / Re-test
Alternate Forms
Internal Consistency◦how items correlate with each other
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Internal Consistency ReliabilitySplit-Half
Kuder-Richardson◦Dichotomous items- right /wrong
Chronbach Alpha ◦Average correlation of all possible
split-half reliabilities
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Parenting Skills Measure: Q 2a-c
a. 12-item measure rx= .70 to rx= .95 among White samples
b. Expected reliability estimates among the Latina sample
c. Three-item measure: rx=.40 to rx=.45
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Parenting Skills Measure: Q 2a
a. 12-item measure: internal consistency reliability coefficients rx= .70 to rx= .95 among White participants
70% to 95% of variability in respondents’ scores is due to
and the rest is due to .
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Reliability Estimates: Q 2aExtent to which variability is
due to true variation versus error ◦ Cronbach alpha =. 70;
70% of variation in scores is due to true differences in parenting skills & 30% is due to error
◦ Cronbach alpha =. 95; 95% of variation in scores is due to true
differences in parenting skills & 5% is due to error
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Parenting Skills Measure: Q 2b
a. 12-item measure rx= .70 to rx= .95 among White samples
b.Expected reliability estimates among the Latina sample
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Parenting Skills Measure: Q 2b
a. 12-item measure rx= .70 to rx= .95 among White samples
b. Expected reliability coefficient among Latina sample =>.70
Yes/No ?
Reliability refers to scores with specific and
. It’s a property of not of instruments.
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Parenting Skills Measure: Q 2b
a. 12-item measure rx= .70 to rx= .95 among White samples
b.Expected reliability coefficient among Latina sample =>.70
No. Reliability refers to scores with specific respondents and conditions
It’s a property of scores, not of instruments 15
Parenting Skills Measure: Q 2c
a. 12-item measure rx= .70 to rx= .95 among White samples
b. Reliability estimates among the Latina sample
c. Three-item measure: rx=.40 to rx=.45. How to improve the scale scores’ reliability.
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Parenting Skills Measure: Q 2c
c. Three-item measure: rx=.40 to rx=.45 –
New items increase reliability only if they are of good quality: validity and reliability
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Reliability and Correlation: Q 5In correlational research, how does the reliability of two scores affect the probability that the observed correlation coefficient between the two scores approximates the “true” correlation coefficient of the constructs?
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Internal Reliability and Correlation
Parenting Skills 1 PSM1 rx = .45
Parenting Skills 2 PSM2 rx = .90
Self-Esteem SE rx = .85
PSM1 (rx = .45) correl. Self Esteem PSM2 (rx = .90) correl. Self Esteem
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Reliability vs. ValidityObserved correlation coefficient
will be smaller and less accurate with the less reliable measure
Correlations between constructs are attenuated by the reliability of the measures
The reliability of a measure puts a ceiling on its validity
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Instruments
1. Description of Measure
2. Validity Estimates
a. Instrument name a. Convergent/Discriminate Validity
b. Acronym b. Validation Sample(s)
c. Authors
d. Key References 3. Reliability Estimatese. Brief description of
construct(s)a. Chronbach’s alpha
coefficient f. Type of measure (e.g self-
report) Previous and Current studies
g. Number of items b. Test/Re-Test
h. Example of items
i. Items response options
j. Factors or subscales
k. Scoring options and direction
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