Table 2 Specification of seven injection devices on the utility values of six attributes that were included in the conjoint model and which were rated the highest in the study

Attribute	Utility	Injection device
Attribute	Utility	A	B	C	D	E	F	G
Operated by	Auto-injector	+	+	+	+	+		+
	Plunger						+
Weight	Like a pencil (10 g)						+
	Like half an apple (50 g)		+		+	+
	Like a standard apple (100 g)							+
	Like a large apple (150 g)	+		+
Sound made	None						+
	Soft (heard by user only)				+	+
	Distinct (heard within 2 m)		+					+
	Loud (easily heard by all those in same room)	+		+
Preparation	No mixing required				+			+
	Mixing required weekly-to-monthly	+	+	+		+	+
Needle	Needle-free	+		+				+
	0.5 cm needle				+
	1 cm needle		+			+	+
Size	9 cm×3 cm						+
	9 cm×6 cm							+
	15 cm×6 cm	+	+		+	+
	15 cm×9 cm			+