methodology 179 human 123 Humans 104 Research Design 85 Methodology 75 Response surface methodology 58 article 54 Article 46 Research 46 male 38 adult 36 female 36 Design/methodology/approach 32 controlled study 32 Malaysia 27 Male 24 Psychological methodology 24 Female 22 procedures 22 Optimization 20 Surface properties 18 algorithm 18 response surface methodology 18 Surveys 17 Adult 15 Decision making 14 Psychology 14 Sustainable development 14 chemistry 14 human experiment 14