Background: Validating a questionnaire/instrument before proceeding to the field for data collection is important.
Methods: An 18-item breastfeeding intention, 39-item attitude and 44-item knowledge questionnaire was validated in a Croatian sample of secondary-school students (N = 277).
Results: For the intentions, principal component analysis (PCA) yielded a four-factor solution with 8 items explaining 68.3% of the total variance. Cronbach’s alpha (0.71) indicated satisfactory internal consistency. For the attitudes, PCA showed a seven-factor structure with 33 items explaining 58.41% of total variance. Cronbach’s alpha (0.87) indicated good internal consistency. There were 13 knowledge questions that were retained after item analysis, showing good internal consistency (KR20 = 0.83). In terms of criterion validity, the questionnaire differentiated between students who received breastfeeding education compared to students who were not educated in breastfeeding. Correlations between intentions and attitudes (r = 0.49), intentions and knowledge (r = 0.29), and attitudes and knowledge (r = 0.38) confirmed concurrent validity.
Conclusions: The final instrument is reliable and valid for data collection on breastfeeding. Therefore, the instrument is recommended for evaluation of breastfeeding education programs aimed at upper-grade elementary and secondary school students.
Keywords: breastfeeding; questionnaire; students.