This study was performed in two stages, including translating the SASS-14 questionnaire from English to Persian and examining the psychometric properties of the SASS-14 questionnaire.
The checklist contained several items, including age, gender, marital status, education, occupation, place of residence, and income.
The SASS-14 questionnaire
This questionnaire was first designed by Martínez et al. (14) in 2021 to screen self-care activities in the COVID-19 epidemic. This questionnaire contains 14 items, coded as a Likert scale from one (never) to six (always). The minimum and maximum scores of the questionnaire are 0 and 84, respectively. The higher scores indicate higher levels of self-care. The SASS-14 consists of four subscales: health awareness (five items); nutrition and physical activity (three items); sleep quality (two items); and social support, interpersonal skills, and leisure activities, which include personal and interpersonal coping strategies (four items).
Satisfaction with life scale (SWLS)
This scale was developed by Diner et al. (1985) and consists of five statements that measure the cognitive component of actual well-being (15). The psychometric properties of the Persian scale were assessed by Bayani et al. in 2007. Its structural validity was assessed via convergent validity using the Oxford Happiness List and Beck Depression Inventory; Cronbach's alpha showed 0.83, and test-retest indicated 0.69 reliability (16).
36-Item Short-Form Health Survey (SF-36)
This questionnaire was developed to assess the overall state of health and disability (17). The score range is between 0 and 100, and higher scores indicate a higher quality of life. The Persian version of this scale showed a good level of validity and reliability in the Montazeri et al.’s study in 2005 (17).
Stage 1: Translation Process
After obtaining written permission, the original version of SASS-14 was translated from English to Persian in several steps. In the first stage, two qualified and independent translators (a Reproductive Health Specialist and an English Language Specialist) translated the original English version into Persian (backward translation). Next, the translations were compared and evaluated in terms of quality, and the most appropriate translation for the phrases was selected to reach a single translation. Then, the final translated version was given to two English Language Specialist who had not seen the original English text in order to translate it from Persian to the original language (back translation) to ensure the accuracy of the translation. Finally, all translations and the original version were reviewed and compared by a panel of experts, and the final Persian version was approved.
Stage 2: Psychometric Properties
Design, participants, and sampling
Participants in this cross-sectional study were selected from the population of different towns in Iran using a convenient sampling strategy from March to November 2021. A link, including study objectives and questionnaires items, was sent via SMS, related groups, and channels available in WhatsApp, Telegram, and Instagram applications. They completed the questionnaire if they met the inclusion criteria. They were also asked to share the questionnaire with other individuals, groups, and channels they knew. The inclusion criteria were willingness to participate in the study, age over 18 years, literacy in reading and writing, and absence of diagnosed mental disorders such as depression, anxiety, and obsession in recent weeks. The subject-to-item ratio method is often used to determine the sample size required for Exploratory Factor Analysis (EFA) (18). There are different recommendations from 2 to 20 people for each item and a minimum sample size of 100 to 250 is suggested (19). Moreover, recommendations in the literature for sample size in Confirmatory Factor Analysis (CFA) vary from 150 to 1000 people (19). In this study, according to the number of items in the questionnaire (14 items), the minimum sample size required was 140 people (10 times the number of items), which was increased to 200 samples in order to comply with the minimum sample size. To perform EFA and CFA on separate samples, reaching 400 samples were targeted.
Eight health experts, one instrumentation specialist, and a clinical specialist (10 people in total) approved the content validity of the final Persian version. To determine the Content Validity Ratio (CVR), a triple Likert scale was chosen (necessary, useful but not necessary, not necessary). The content validity of each item was confirmed if it had a CVR > 0.62, according to the Lawshe table. To determine the Content Validity Index (CVI), each expert was asked to consider relevance, clarity, simplicity, and ambiguity for each item using a 4-point Likert scale; questions with CVI > 0.79 were considered appropriate.
Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) were used to evaluate the construct validity. For this purpose, the data were first randomly divided into two equal parts. The first sub-sample (n = 200) was used for EFA, and the second sub-sample (n = 200) was used for CFA. Before performing EFA and CFA, the multivariate normality assumptions were tested using skewness and kurtosis values and chi-square versus Mahalanobis distance plot. The values of Skewness and Kurtosis between − 2 and + 2 and the placement of points on a straight line in the graph indicate the normality of the data (20). The presence of multicollinearity was also assessed by Variance Inflation Factor (VIF); VIF < 3 was considered as the absence of multicollinearity (21).
Data adequacy for EFA was also assessed using Bartlett’s test and the Kaiser-Meyer-Olkin index (KMO). Significance (rejection of null hypothesis) in Bartlett’s test and KMO value above 0.7 was considered acceptable (22). Principal Component Analysis (PCA) and Varimax rotation were used to extract the factors. Based on the assumption that the scale is not one-dimensional, the number of factors was considered 4 according to the number of factors in the original version of the scale. The adequacy of the number of factors was evaluated based on special values greater than one using Scree diagrams. Items with a factor load greater than 0.5 and with a minimum difference of 0.2 with other factors were retained (23). CFA was done on the second sample based on the factors extracted from the EFA model (based on the maximum likelihood estimation). The model fit indices, including \(\chi 2/df,\) Goodness-of-Fit Index (GFI), Adjusted Goodness-of-Fit-Index (AGFI), Comparative Fit Index (CFI), Tucker-Lewis Index (TLI), Root Mean Square Error of Approximation (RMSEA) and Normed Fit Index (NFI) were also evaluated.
To determine the convergent validity, along with SASS-14, SWLS and SF-36 were completed without time interval by the participants. Then, the correlation coefficient between the responses of these scales was determined and calculated. Correlation coefficients were determined as follows: less than 0.1 weak, between 0.1 to 0.5 moderate, between 0.5 to 0.8 strong, and values greater than 0.8 as very strong (24).
The reliability of the Persian SASS-14 questionnaire was assessed using Cronbach's alpha coefficient method and test-retest method with an interval of two weeks between 30 people. A Cronbach's alpha value between 0.6 and 0.7 indicates an acceptable level of reliability and a value greater than or equal to 0.8 indicates good reliability (25). Test-retest reliability was determined using the Intraclass Correlation Coefficient (ICC) and values greater than 0.75 were considered good reliability, between 0.5 to 0.75 moderate, and less than 0.5 as poor (26).