Research design, context and participants
This exploratory psychometric study was conducted in Beiragh in 2018, after receiving approval from the Ethics Review board at Tarbiat Modares University. Beiragh is a village, located in the northern slope of Sahand Mountain in the south of Tabriz metropolitan city. About five thousand people live in Beirgh. For the most part, Beiraghian's employment and economic growth depends on their livestock. The main job of Beiraghians is livestock husbandry and most of the country's dairy products are produced in villages such as Beiragh. Beiraghians raise mainly sheep and goats and rarely cows and their animals are vaccinated by two veterinarians and two livestock vaccinators each year, without paying any charge.
The details for the participants in each phase of this psychometric study are explained in Table 1.As it is shown in Table 1, different participants were recruited depending on the study phase.
It was very important to choose specialists who had valid articles in the mentioned field or had work experience in this area. Therefore, we tried to invite experts from different groups with the above mentioned qualifications to help in generating items, finalizing the first draft of the questionnaire and evaluating face and content validity of the items [20, 21]. Livestock breeders were invited to participate in generating items and evaluating their face and construct validity. All livestock breeders were male. Details for recruiting livestock breeders in each phase are described later.
Developing the first draft of the questionnaire
Initial items of BPQ were achieved through a thorough literature review and interviews with all stakeholders. Databases, including MEDLINE, PubMed, EMBASE, ERIC, Cochrane Library and Cumulative Index of Nursing and Allied Health Literature (CINAHL) were searched to find any published study about brucellosis prevention or animal vaccination. A combination of keywords of "prevent*", "brucella*" and "vaccine*" were used to search in English and Persian. 816 published articles between 2008 and 2019 were obtained and after reading their abstracts and removing duplicate articles, 110 more relevant articles were read in full text. Having reviewed those papers and contacted the corresponding authors, nine Persian and three English questionnaires were obtained[15–17].
Interviews were conducted to identify the factors influencing preventive behavior of livestock breeders. The conceptual framework for conducting the interviews was the concepts from the first four phases of PRECEDE model [14]. Purposive sampling was employed to recruit participants [18] and directed content analysis was used to analyze the content of the interviews [19].
livestock breeders, health educationists, veterinarians and experts from a vaccine providing institute in the region, who were volunteer, participated in 30 to 45 minute face-to- face interviews. The interviews took place at participants' desired time and place. They were told that their information would be kept confidential and would be used anonymously. The items from literature review were combined with the findings from interviews. Later, health educationists, veterinarians and experts from a vaccine and serum production institute were asked to participate in three focus group discussions. Each session lasted 90-minutes. One of the research team members acted as the coordinator of the sessions and notes were taken by another member of the team. Then, a directed analysis was performed on the interview content. Identical and duplicate questions were removed and some questions were edited. The first draft of the research questionnaire was confirmed. Anchor response of the items were discussed and finalized by the research team members as well.
Assessment of face and content validity of the questionnaire
Face validity was examined both qualitatively and quantitatively. For qualitative assessment, based on the feedback from livestock breeders and health educationists, any ambiguity in the meaning, wording and scaling of the items, grammatical errors and errors in items allocation, were identified and resolved. For quantitative assessment, impact score (IS) of each item was calculated.
Livestock breeders and health educationists participated to assess the face validity of BPQ. Those livestock breeders were different from the ones, who participated later in assessing the construct validity of BPQ and those in the cross-sectional part of the study.
To evaluate the face validity of the items, the appropriateness of each item was rated by an expert, using a five-point Likert scale. Impact score of each item was calculated by the formula of:
Impact Score = Frequency (%) × Importance [22, 23]. Frequency” in this formula is the number of patients, who rated the appropriateness of the item 4 or 5, while “importance” was the mean score of the item on a 1–5 rating scale.
Content validity of the questionnaire was also examined both qualitatively and quantitatively. For quantitative assessment of content validity, Content Validity Index (CVI) and the Content Validity Ratio (CVR) were calculated. To do so, BPQ was submitted to twenty experts. In this phase, BPQ was emailed to twenty veterinarians and health educationists to evaluate the content validity of the questionnaire. One expert did not complete the questionnaire and concerning the precision of the data, two questionnaires were set aside. (Response rate= 0.85%).
CVI and CVR were calculated based on three and four part Likert scales, respectively. CVR was calculated by the formula of (Ne – N/2)/ (N/2) [23]. In this formula, N is the total number of panelists and Ne is the number of panelists who rated the item to be “essential”. Based on the Lawshe table, items with CVR below 0.46 were removed [24].
To calculate the CVI of the items, relevance of each item was rated by a 4-point Likert scale, by the formula of (CVI=the number of specialists who assigned scores 3 and 4 to the items/N).
Items with the CVI less than 0.79 were removed [25, 26].
Assessment of construct validity of the questionnaire
Construct validity of the questionnaire was evaluated by both exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). It is recommended to perform each of EFA or CFA, by participation of at least 200 participants from the target group [27]. Sampling framework in this phase of study included 2122 livestock breeders, who were living in Beiragh. Due to the fact that livestock breeders deliver their dairy products to the dairy producing local mini-factories in the region, the complete list of the whole livestock breeders was taken from forty cheese producing mini-factories in Beiragh. Considering the 10-15% drop rate in the previous relevant studies, 50 more participants were needed [27, 28]. Four hundred and fifty livestock breeders in Beiragh were randomly selected and invited to participate at this phase. Random sampling of the list was performed using
(www.randomizer.org software ).
Exploratory Factor analysis (EFA)
EFA was done on 42 binary items and 17 Likert-scale items, which were intended to explain preventive behavior of livestock breeders. Principal component analysis and oblimin rotation method were used to determine the number of optimal factors. Loadings with the significance lower than 0. 5 were excluded from the analysis [29]. If an item was loaded into different factors, it was related to the factor in which it had the largest factor loading. After the analysis was completed, the items were categorized and each category formed a construct or factor. Later, the extracted factors were named by team members, according to the nature of its containing items and based on the characteristics they are proposed to measure.
For the items with binary response anchors, the generalized confirmatory factor analysis [30] and WLSMV statistical estimation method were used [30]. The software of M-Plus- version 7.4 was applied to test and evaluate the intended conceptual model. Based on the factors, which were identified by the EFA and considering the hypothetical relationships among the factors, a conceptual model was proposed to be tested. Fifty nine items were categorized into three factors of awareness, attitude and practice. Due to the lack of proper fitness of the initial three-factor conceptual model, the factor of the awareness was divided into three sub-categories: direct awareness; indirect awareness and vaccine awareness. The proposed new conceptual model with 59 questions and 5 latent factors (direct awareness; indirect awareness, vaccine awareness, attitude, and practice) was evaluated by confirmatory factor analysis. After removing items with low factor loadings, the final model with five factors (behavioral constructs) and 53 items was confirmed.
The fitness of the proposed model was assessed by fit indices including the ratio of Chi-square to degrees of freedom (X2/DF), Root Mean Square Error of Approximation (RMSEA), Comparative Fit Index (CFI), and Tucker-Lewis Index (TLI). The values of at least 0.90 for CFI and TLI, and below 0.08 for RMSEA represented a good fitness [31, 32]. After excluding non-significant items, the final conceptual model was introduced.
Assessment of reliability of the questionnaire
Cronbach’s alpha coefficient and composite reliability (CR) were calculated for testing the internal consistency of the questionnaire. Stability of the results was examined by calculating the Interclass Correlation Coefficient (ICC) [23,24].Considering the point that About 30-40 participants are required to evaluate reliability[35], forty two volunteer livestock breeders completed the research questionnaire twice in a two- week interval. By so doing, the stability of the results was measured [34]. For the analysis of the absolute reliability of the results, standard error of measurement (SEM) was calculated. The IBM SPSS statistics version 24 was used to perform data cleaning and calculating reliability indices. P values lower than 0.05 were considered significant.