Understanding Reliability in Psychological Testing

• Reliability is synonymous with dependability or consistency in measurement
• Reliability refers to consistency in measurement, producing similar results, and is not an all-or-none matter, as a test may be reliable in one context but unreliable in another
• The Reliability Coefficient is a statistic quantifying reliability on a scale from 0 (not at all reliable) to 1 (perfectly reliable)
• Error usually refers to a preventable mistake due to lack of conscientiousness, skill, or information
• Measurement error refers to the inherent uncertainty in any measurement, and still occur even when procedures are followed perfectly
• True scores cannot be observed directly, they are a useful fiction that allows us to understand the concept of reliability more deeply
• True scores can be approximated via averaging many measurements
• When measuring something repeatedly, time elapses between measurements and the act of measurement can interfere with accurate measurement.
• Carryover effects are measurement processes that alter what is measured
• Practice effects are instances where tests themselves provide additional test taking practice
• Fatigue effects are cases where repeated testing reduces overall mental energy
• The Long-term average of these estimates is called the true score
• True score isnt necessarily the truth
• A person's true depression score on one measure will differ from their score on another depression measure
• Reliable tests give scores that closely approximate true scores
• Construct score is truth independent of measurement
• Construct Score pertains to a theoretical variable such as depression
• It entails a person's standing on a theoretical variable independent of any measure
• Valid tests give scores that closely approximate construct scores
• "The true score and the construct score would be identical"
• Observed Score is symbolized as the amount after observing the test
• The observed score X and the true score T will likely differ by some amount because of measurement error
• This amount of measurement error will be symbolized by the letter E
• The observed score X is related to the true score T and the measurement error score E with this famous equation: X = T + E.
• Variance is a statistic useful in describing sources of test score variability and standard deviation squared.
• True Variance is variance from true differences
• Error Variance is the variance from irrelevant, random sources and may increase or decrease a test score by varying amounts
• Consistency of the test scores, and thus the reliability can be affected
• Reliability refers to the proportion of the total variance attributed to true variance
• The greater the proportion of the total variance attributed to true variance, the more reliable the test.
• True Differences are assumed to be stable and yield consistent scores on repeated administrations of the same and/or equivalent forms of tests.
• Random Error consists of unpredictable fluctuations and inconsistencies of other variables in the measurement process.
• It is referred to as "noise," this source of error fluctuates from one testing situation to another with no discernible pattern that would systematically raise or lower scores.
• Systematic Errors do not cancel each other out because they influence test scores in a consistent direction
• Systematic errors either consistently inflate scores or consistently deflate scores
• Once a systematic error becomes known, it becomes predictable as well as fixable, and It does not affect score consistency
• Bias is the degree to which a measure predictably overestimates or underestimates a quantity and measurement

Sources of error variance

• Test construction is one source of variance during test construction is item sampling or content sampling
• Terms that refer to variation among items within a test as well as to variation among items between tests
• Test administration includes sources of error variance such as attention and motivation
• Examiner-related variables are potential sources of error variance relating to the examiner's appearance, demeanor, presence or absence
• Computer-scorable items have virtually eliminated error variance caused by scorer differences.
• Other sources of error include surveys plus or minus a margin of error that the researchers estimate to exist in their study
• Surveys and polls are two tools of assessment used by researchers who study public opinion

Reliability estimates

• Test-retest reliability estimates can be obtained by correlating pairs of scores from the same people on two different administrations of the same test
• A Test-retest estimates are used to see if measures are relatively stable over time
• The longer the time that passes, the greater the likelihood that the reliability coefficient will lower
• evaluation of a coefficient must extend to internal and external motivations and conditions

Parallel forms

• The degree of the relationship between various forms of a test
• Can be evaluated by means of an alternate-forms or parallel-forms coefficient of reliability
• Parallel forms exist when, for each form of the test, the means and the variances of observed test scores are equal.
• Parallel forms reliability refers to which the errors have affected test scores and which the correct scores were
• Estimating it is straightforward, by calculating the correlation between scores from a representative sample of individuals who have taken both tests. Time-consuming and expensive
• Two test administrations with the same group are required Test scores may be affected by factors such as motivation, fatigue, or intervening events such as practice, learning, or therapy.
• Internal Consistency Estimate of Reliability is used to estimate inter-item consistencies without having to administer the test twice

Split-Half Reliability Estimates

• Obtained by correlating two pairs of scores obtained from equivalent halves of a single test administered once
• Split test into equivalent halves and adjust with spearman-brown formula
• One acceptable way to split a test is to randomly assign items to one or the other half of the test, known as odd/even reliability
• The test may also be split by content, to so each half contains items equivalent with respect to content and difficulty
• Reliability increases as test length increases
• Reduction in test size may be indicated in situations where boredom or fatigue could produce responses of questionable meaningfulness.
• Another way to measure internal consistency is via inter-item measure, by calculating from single administration
• Coeffcient alpha can be though of as the mean of all possible split-half correlation, and are good for determining how similar sets of data are
• The test has four items, with each item being the sum of a true core and different error term
• Many statisticians use McDolald's omega to measures reliability, which accurately estimates interal consistency
• Inter-Score Reliability is the degree of agreement or consistency, often used when coding nonverbal behavior
• This can be improved via study with practice tests to improve overall accuracy
• Can measure this with Inter-Score coeffcient, but determining the degree of consistency among scorer s in the scorig of testes to calculatin the coeffcient
• Various tests could be useful for various testing purposes

Nature of the test

• Internal consistneacy is a reilable way to measure, although a common issue is that the measure itself has to be homogenous or heterogenous
• The chereacteric in meausre most be dynamic and or static,
• Restriction occurs if the variance or analsysis is stricted by sampoling, but increased is due to lower coefficiant
• If the variance of either variable in a correlational analysis is inflated by the sampling procedure, then the resulting correlation coefficient tends to be higher. Critical importance is whether the range of variances employed is appropriate to the objective of the correlational analysis
• Powers test must be long enough to give takers enough time to complete, whereas Speed test have ver limited time and not all can complete

True value and theory

• The True Store in Classical Testing is commonly used, with focuso on Intuitive appeals in measuremnt, and is simply understood
• CTT assumes application in most situation as its rather straight forward with irt, allow for advantages as ctt is a good fit to the context needed.
• Domain Sampling Theory seekk to estimate varying degree and conditions to test scores, conceiving that to be reliability with defined parameters
• Domain of behavior share characterisitc and thought to have varying means
• Generalizability study based on the idea that a person's test scores vary because of testing scenarios, by the use of a Generalizabiltiy study, which can use facets to alter factors like itme count, purposes, etc
• Can measure useful factors and how dpendable scores for different conditions,
• Finally there si IT, it is the abiltiy for someone with test taking abiltiy to follow and be more reliable, also known as latent trait. There are some different styles of measurement. It can work to assess degree, and be helpful in tests where there is questions with one or two answers such as true false.
• The confidence interval can give a proper estimated range of score, that indicates how much confidence the test taker has to test

SEM/SEMm

• SEM gives measure and precision to obseverdd test sc ores,
• The error could exist due to any number of variables
• The related differences and errors can be measured to get more helpful testing with different error and values related.

Explore the concept of reliability in measurement, focusing on its definition, the reliability coefficient, and the distinction between error and measurement error. Learn about true scores and the challenges of repeated measurements. Also, understand how carryover effects can impact reliability.