Tool set-up in Qualtrics
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The online tool was developed using Qualtrics (Qualtrics, Provo, UT, USA, 2022), an online survey development software. Image-series for all test foods were included in the food image section. In this section, the eight successive images were displayed to correspond with the sliding scale question, ‘What portion size of (the test food and setting; for example, sweet biscuits as a snack) would you normally eat?’. The sliding scale was labelled from smallest ‘1’ to largest ‘8’ plus the additional selections of ‘0 – I do not eat this food’ and ‘9 – greater than the largest option displayed’ (Fig. 