In confirmatory factor analysis (CFA), which is used quite often for scale development and adaptation studies, the selected estimation method, affects the results obtained from the data. Because of the selected estimation method, the model parameters and their standard errors, and the model data fit values may alter the results substantially. So that, the purpose of this research is to compare the performance of different estimation methods for CFA. Maximum likelihood (ML), unweighted least squares (ULS) and diagonally weighted least squares (DWLS) are used in this research as estimation methods. These methods are applied in data sets and regression coefficients and their standard errors, t values, fit indexes and iteration numbers obtained from these estimation methods are examined. As a result, ULS method can converge with the minimum number iterations and it seems to be the more accurate method for estimating the parameters.
Stress is defined as a person's interaction with their environment that is thought to threaten or affect an individual's potential, resources, and well‐being. The most popular instrument to assess perceived stress is the Perceived Stress Scale (PSS). Therefore, making a systematic review of studies testing the internal structure of PSS and conducting a Meta‐Analytic Confirmatory Factor Analysis (MACFA) on the database created with the information obtained from these studies are the aims of this research. A total of 76 samples from 57 unique studies were included in this database using various inclusion criteria (total N for PSS‐14 = 28,632, for PSS‐10 = 46,053). The correlated two‐factor model for PSS was confirmed by MACFA performed on the pooled correlation matrix generated by the random effects meta‐analysis. Findings of dimensionality analyses, factor loadings, omega values, and measurement invariance showed that the model that best explained the factor structure of PSS was the correlated two‐factor model. The strict measurement invariance of the PSS was achieved across age and clinical status, and the internal consistency was high according to the omega values. Several recommendations moving forward are discussed.
The aim of this review is to explain the methods that can be used when developing short form of a measurement tool and to examine some short form development studies in the field of health sciences literature by taking into consideration the criticisms of short form development studies. It is seen that short form development studies are especially concentrated in the fields of health sciences. The main reason for this situation has been shown that clinicians need fast and reliable measurement tools to reduce the pressure on them. The review results of the 12 articles selected for this research show that there are very few studies that follow the guidelines for short form development. Researchers are advised to develop the short form of the scale by taking into account the criteria mentioned in this study. It is recommended to select measurement instruments which are developed in accordance with ethical rules and have sufficient psychometric properties. Clinical researchers should be aware that the perception that measuring instruments containing less items are less valid does not show the truth. The same psychometric standards are sought for each measurement tools.
Bu çalışma, Madde tepki kuramının farklı uygulamalarından elde edilen parametrelerin ve model uyumlarının örneklem büyüklüğü ve test uzunluğu açısından karşılaştırılması isimli doktora tezinden üretilmiştir.
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