Mahir KutayTuncay ErcanErcan, TuncayKutay, Mahir2025-10-0620151976-727710.3837/tiis.2015.02.0202-s2.0-84924203638http://dx.doi.org/10.3837/tiis.2015.02.020https://gcris.yasar.edu.tr/handle/123456789/6113https://doi.org/10.3837/tiis.2015.02.020Trust and trustworthiness of web services and organizations is calculated as scalar values. But there is still a certain level of risk for the overall reliability of this value. In this article we focus on calculating trust values as intervals between upper and lower bounds based on predefined confidence values through an additional confidence probability. This will give us a more realistic approach to the trust assessments between individuals and organizations. We also developed a web-based software tool TAST (Trust Assessment Software Tool) that collects the web services' evaluation of different customer groups for similar organizations through the user interface and calculates the trust intervals for predefined and previously selected confidence values. Our model uses a weighted calculation of mean and variances of customer groups in specific periods and analyses the total and incremental trust of different customer groups.Englishinfo:eu-repo/semantics/openAccessTrust and trustworthy, reliability, confidence probability, TASTTASTConfidence ProbabilityTrust and TrustworthyReliabilityArticle