Questions and Answers
What is the field of study concerned with the measurement of psychological attributes and characteristics?
What is the purpose of psychometrics?
To design and evaluate reliable and valid psychological measures
What does Classical Test Theory rest on?
True scores
What is a true score (T)?
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Classical Test Theory assumes T is ____ distributed on a normal distribution.
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An alternative way to think about the true score is to imagine an individual taking the same test ____ number of times.
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How do we infer the values of true scores?
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What will the observed score be?
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The discrepancy between true and observed scores is known as ____ error, denoted e.
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What is the observed score equation?
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What is measurement error?
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Match the following measurement error assumptions:
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What does the mean of the error term being 0 imply about the mean of the true scores?
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What is the expected variance of the observed score?
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What is the Standard Error of Measurement (SEM)?
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If an individual took the same test an infinite number of times, SEM would be the ____ of their collected scores.
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What is reliability in Classical Test Theory (CTT)?
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How can we define reliability?
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What can reliability be thought of as?
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What is test-retest reliability?
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What is an estimate of reliability?
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What does Classical Test Theory definition of reliability assume?
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What is split-half reliability?
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What is Cronbach's alpha (alternative formula)?
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What does the alternative formula for Cronbach's alpha make clear?
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What tends to happen to reliability with more items?
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What are Cronbach's alpha scores?
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What do the reliabilities of 2 measures place constraints on?
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What happens if you have 1 or 2 poor measures?
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What is validity?
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What is face/content validity?
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What is criterion validity?
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What is concurrent validity?
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What is predictive validity?
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Correlations are used to assess the degree of ____ validity of a measure.
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What is construct validity?
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What is convergent validity?
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What is discriminant validity?
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What does a multitrait-multimethod matrix measure?
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What does monotrait-heteromethod index?
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What does heterotrait-monomethod reflect?
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What are two basic ways items can differ?
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How is item difficulty defined for dichotomous items?
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What does item discrimination compare?
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What are the 3 basic ways to measure item discrimination?
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What does the Extreme Group Method involve?
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What is Item Total Correlation?
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What can Inter-Item Correlation show?
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What is the Item-Characteristic Curve?
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What are the steps of drawing an Item-Characteristic Curve (ICC)?
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_____ slopes mean an item is more discriminating than _____ slopes.
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What is Item Response Theory?
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What are the advantages of Item Response Theory?
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In ICC, what does p stand for?
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What does high discrimination mean?
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What is the Test Information Function?
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What does Item Response Theory show?
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What is an example of Differential Item Functioning (DIF) Analysis?
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Study Notes
Psychometrics
- Field dedicated to measuring psychological attributes and characteristics.
- Aims to develop reliable and valid psychological assessments.
Classical Test Theory (CTT)
- Fundamental premise is the concept of true scores, representing an individual's score without measurement error.
- True scores are assumed to be normally distributed within the population.
- Infers true scores by calculating observed scores through testing.
Measurement Concepts
- Observed scores (X) are derived from the true score (T) and measurement error (e), represented by the equation X = T + e.
- Measurement error reflects discrepancies between true and observed scores, influenced by various factors like fatigue or distractions.
- Assumptions include random distribution of error, zero expected value of error, and no correlation between true scores and errors.
Reliability
- Defined as the consistency and precision of measurement in assessments.
- High reliability indicates that test items reliably represent the overall construct being measured.
- Calculated as the proportion of observed score variance attributed to the true construct.
Types of Reliability
- Test-retest reliability measures consistency of scores over time.
- Split-half reliability assesses internal consistency by correlating scores of two halves of the same test.
- Cronbach's alpha is a reliability coefficient, with values above 0.7 deemed acceptable, and above 0.9 indicating potential redundancy.
Validity
- Validity gauges whether a test effectively measures what it is intended to.
- Includes face/content validity, criterion validity (subdivided into concurrent and predictive validity), and construct validity.
- Construct validity examines correlations between similar and dissimilar constructs, emphasizing convergent and discriminant validity.
Item Analysis
- Items may vary based on difficulty (how many can answer correctly) and discrimination (how well they correlate with total test performance).
- Item-Characteristic Curve (ICC) visually represents the success rates on test items against total scores.
- Item Response Theory (IRT) enhances measurement by accounting for how individual traits influence responses.
Differential Item Functioning (DIF)
- Analyzes how different groups respond to test items, important for ensuring fairness.
- Example: May identify performance differences between genders on specific test items even when abilities are equal.
Summary of Key Methods
- Extreme Group Method evaluates item discrimination by analyzing performance in the highest and lowest scoring groups.
- Item-Total Correlation assesses an item’s effectiveness by correlating it with total test scores.
- Inter-Item Correlation shows how items relate to one another, facilitating identification of strong or weak items in an assessment.
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Description
Explore the fundamental concepts of psychometrics, including the principles of classical test theory (CTT) and measurement concepts. This quiz will assess your understanding of true scores, observed scores, measurement error, and the importance of reliability in psychological assessments.