intratester

Intratester refers to a person who conducts a test or assessment. In the context of measurement reliability, intratester reliability (also called intra-rater reliability) describes the consistency of this tester’s measurements when the same subject is assessed on multiple occasions under similar conditions.

Intratester reliability is one facet of measurement reliability, alongside intertester reliability, which concerns consistency between different testers. High intratester reliability is desirable because it indicates that the tester applies the protocol consistently over time, reducing random variation due to the tester rather than the subject or the measurement instrument. Factors that influence reliability include clear testing protocols, tester training, equipment calibration, and standardized testing environments. Blinding the tester to prior results and scheduling tests to minimize fatigue or learning effects can also help.

Assessment typically involves repeated measurements on the same subjects. For continuous data, statistics such as the intraclass correlation coefficient (ICC) and the standard error of measurement (SEM) are used to quantify agreement and precision. Bland-Altman plots can illustrate agreement across repeats. For categorical data, Cohen’s kappa or weighted kappa may be appropriate. The minimal detectable change (MDC) can help interpret whether observed changes exceed measurement error.

Improving intratester reliability involves developing and following standard operating procedures, providing comprehensive training, using clear scoring rubrics, and implementing regular calibration and quality-control checks. Limitations include sample size, time between measurements, and potential learning or fatigue effects that can still influence results.