The present cross-sectional methodological study was conducted in two qualitative and quantitative phases. In the first phase of the research, the main aspects of the concept of professional discrimination were defined through extensive literature review and the viewpoints of experts and nurses. In the second phase, after designing and extracting the pool of items, the validity (face, content, and structure) and reliability (internal consistency and stability) of the questionnaire were assessed.
Phase I. Explaining the concept of professional discrimination
In this phase, articles were sampled and searched using search engines in electronic databases as well as manual searches in libraries, resources, and related research. To investigate published studies in Iran, Medlib, Iran Medex, Magiran, SID, and Irandoc databases were searched without time limit using the following keywords: discrimination, professional discrimination, justice, and instrumentation (scale or measure). The following sites were also searched for reviewing the studies performed in other countries: Google Scholar, CINAHL, PubMed, MEDLINE, ProQuest, Ovid, Elsevier, and Wiley. The inclusion criteria were relevance to the study and publication in English or Persian. Quantitative, qualitative, and review studies were included and keywords were searched for in the titles, keywords, or abstracts. Scientific articles had to be in the journals whose articles were peer-reviewed. Other formal studies were reviewed if they were published in books, including books on the concept of discrimination and professional discrimination. At the end of this phase, the concept of professional discrimination was defined, its dimensions and subscales were determined, and the pool of items was formed.
Phase II. Psychometric evaluation of the professional discrimination scale
- Determining the validity of the tool:
1- A) Face validity: Face validity was evaluated in both qualitative and quantitative terms. Considering the qualitative face validity of the questionnaire, to evaluate the rationality, appropriateness, attractiveness, and logical sequence of the items, face-to-face interviews were performed with the participants (19 nurses). After correction of the inappropriate items, in order to reduce and eliminate the inappropriate items and determine the importance of each item, quantitative face validity was assessed by calculating the Importance Score (IS). In doing so, 20 experts were asked to assign a score to each item using a five-point Likert scale ranging from ‘very important’ to ‘not important at all’. Then, the IS for each item of the questionnaire was calculated as follows:
Importance × frequency = Impact score
If this score was more than 1.5, the subsequent analyses would be appropriate and the item would be maintained (29).
1-B) Content validity: Content validity was analyzed in both qualitative and quantitative ways. In doing so, 19 nursing instructors, nurses, and healthcare managers were asked to express their views on the appropriateness of the content of the tool in terms of “grammar compliance, use of appropriate words, placement of items in rightful place, and proper rating”. Considering the quantitative content validity, 15 experts in nursing, psychiatry, and literature were asked to judge the content validity of the instrument based on Waltz and Bausell’s (1983) Content Validity Ratio (CVR) and Content Validity Index (CVI). In this regard, they were requested to examine whether the presence of the items was necessary or not using a three-point spectrum (necessary, useful but not necessary, and not necessary). Then, the following formula was used to calculate the CVR for each item:
Afterwards, the results were compared to Lawshe table. If the calculated number was greater than the table number, the existence of the item was considered necessary (30).
To calculate the Item-Content Validity Index (I-CVI), the experts were asked to score each item based on the three criteria of “relevance”, “clarity”, and “simplicity” on a four-point scale. If the item scored more than 75% in relevance, its “clearness” and “simplicity” were evaluated, as well. The content validity of the whole tool was also calculated. In this context, the Scale CVI/Average (SCVI/Ave) criterion was measured. In order to evaluate the CVI, the modified Cohen kappa was computed as the indicator of agreement among the evaluators. Modified kappa with cut-off points ranging from 0.4 to 0.59 as poor, 0.6 to 0.74 as good, and more than 0.74 as excellent was accepted in this study (31, 32).
1-C) Construct validity: In this study, exploratory factor analysis was used to determine the construct validity of the questionnaire. The number of samples required in factor analysis varies from three to ten per item (33, 34). Therefore, the study sample consisted of 600 nurses who were randomly selected from all the hospitals affiliated to Shiraz University of Medical Sciences. The inclusion criteria were having A.D., B.Sc., and M.Sc. degrees in nursing and having at least one year of clinical experience. Prior to factor analysis, Kaiser-Meyer-Olkin (KMO) test was performed for sampling adequacy. Moreover, Cronbach’s alpha coefficients of the questionnaire and its subscales were calculated by Intra-Cluster Correlation (ICC). Then, the BT correlation matrix of the variables was evaluated. The variables with a correlation coefficient less than 0.3% were excluded (35, 36). In factor analysis, after calculating the correlation matrix, the highly correlated variables were grouped into one category or factor. Afterwards, scree plot values were used to extract the factors of the professional discrimination instrument. The factor load of more than 0.4 was considered in the present study.
- Reliability: The stability and internal consistency of the questionnaire were assessed in this study.
2-A): Internal consistency: Cronbach’s alpha was measured to determine the internal consistency of the questionnaire. Accordingly, scores equal to or greater than 0.7 were considered to be acceptable (35).
2-B) Stability: Stability refers to achieving the same scores in a group of people in two stages (34). In this study, the stability of the questionnaire was assessed via the test-retest method. In doing so, the questionnaire was distributed among 30 participants and completed for the second time within two weeks. The reliability coefficient was calculated by Pearson’s correlation coefficient and ICC. If the ICC index was higher than 0.8, the stability was favorable. All data analyses were carried out using the SPSS statistical software, version 24.
Ethical considerations: This study was approved by the Ethics Committee of Shiraz University of Medical Sciences (code: IR.SUMS.REC.1398.988). Informed consent forms were obtained from the study participants. They were informed that the data would be used solely for the benefit of the participants. They were also assured about the anonymity of their data.