A. 2 Psychometric Properties & Error

Psychometric Properties

Refer to the technical qualities and characteristics of psychological tests and assessments that determine their scientific soundness and practical usefulness

Psychometric Properties

These properties are crucial for ensuring that a test is measuring what it intends to measure, that its results are consistent, and that the scores can be meaningfully interpreted

Reliability

The degree of consistency in measurement in a test

Reliability Coefficient

An index of reliability, a proportion that indicates the ratio between the true score variance on a test and the total score, ranging from 0 to 1

Validity

The degree to which a test accurately measures what it intends to measure

Validity coefficient

An index of validity, ranging from 0 to 1

More reliable

The greater the proportion of the total variance attributed to the true variance, the test is considered…

Goals of Reliability

Estimate errors in psychological measurement. Device techniques to improve testing so errors are reduced

Variance

Useful in describing sources of differing test scores between individuals

True & Error

Types of variance

True Variance

Variance wherein different scores come from the test takers’ varying skills, abilities, or traits

Error Variance

Variance wherein different scores come from environmental distractions, guessing, or the state of the test taker

Measurement Error

It is the difference between a person’s observed score and their true score

Random Error

Source of error in measuring a targeted variable caused by unpredictable fluctuations and inconsistencies of other variables in the measurement process. It is unavoidable

Systematic Error

Source of error in measuring a variable that is typically constant or proportionate to what is presumed to be the true value of the variable being measured. It is avoidable if corrected

Item Sampling/Content Sampling Error

Error that comes from the variation among items within a test and between tests

Test Environment Error

Error that can come from physical variables from the environment such as room temperature, level of lighting, and noise

Test taker variable

Error that comes from variables in the test taker such as emotional problems, physical discomfort, and lack of sleep

Examiner-related variables error

Error that comes from variables in the examiner/proctor such as physical appearance, demeanor, and professionalism