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Reliability of Selection Measures. Reliability Defined. The degree of dependability, consistency, or stability of scores on measures used in selection. Error of Measurement . Obtained Score True Score Error Score. Errors of Measurement.
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Reliability Defined The degree of dependability, consistency, or stability of scores on measures used in selection
Error of Measurement Obtained Score • True Score • Error Score
Errors of Measurement -Physical characteristics = Higher reliability (HR) -Psychological attributes = Lower reliability (LR) ================================== • Large amounts of measurement error = LR • Small amounts of measurement Error = HR
Methods of Estimating Reliability • Examines two sets of measure • If scores from the two measurements are similar, reliability will be raised • If scores from the two measurements are dissimilar, reliability will be lowered
Methods of Estimating Reliability • Statistical procedures calculated reliability coefficients range from 0.00 to 1.00 • Higher the coefficient, the less the measurement error, and the higher the reliability estimate • Lower the coefficient, the higher the measurement error, and the lower the reliability estimate
Methods of Estimating Reliability Selecting a method: • Dependability of data collected today be reflective of the same person in the future • To what degree do evaluations vary from one another • Accuracy of scores on measuring the true ability • Dependability of an assessment of a measure at a given moment
Methods of Estimating Reliability Test-Retest Same measure is used to collect data from the same person at two different times • The higher the coefficient, the greater the approximation to the true score: closer to 1.00 • The lower the coefficient, the greater likelihood of error: closer to .00
Methods of Estimating Reliability Test-Retest – Sources of error • Memory • Learning • “True change”
Methods of Estimating Reliability Parallel or Equivalent Forms Does not use the same measure twice but will instead use equivalent versions of the measure • Each has same number of questions • Each has same level of difficulty • Averages of scores are the same
Methods of Estimating Reliability Internal Consistency Estimates How similar are different parts of the measure (e.g. different questions on a test) in what they measure? • Split-half reliability • Kuder-Richardson Formula 20 • Coefficient Alpha (α) – most commonly reported
Factors Influencing The Reliability of a Measure • Method of Estimating Reliability • Individual Differences Among Respondents • Length of a Measure • Test Question Difficulty • Administration of a measure
Standard Error of Measurement Useful applications: • Forces us to think of scores on a measure not as exact points • Aid in decision making in which only one individual is involved • Determine the magnitude of how scores differ significantly from one another