Table 1.

Correlations between sugar-sweetened beverage theory of planned behaviour single-item indicators and multi-item scales (n = 151).

Construct	Number of questions in multi-item scale	Cron-bach’s α	Sample size	Questionsa	Pear-son’s Correla-tionb
Behavioural intentions	2	0.83	151	You plan to limit your sugary drinks to less than 1 cup each day. Disagree/agree How many days per week do you intend to limit your sugary drinks to less than 1 cup? 0–7	n/a
Perceived behavioural control	3	0.68	151	Limiting your sugary drinks to less than 1 cup of sugary drinks each day if you wanted to do so would be: Easy/difficult You have complete personal control over limiting your sugary drinks to less than 1 cup each day, if you really wanted to. Disagree/agree Limiting your sugary drinks to less than 1 cup each day is mostly up to you if you wanted to. Disagree/agree	0.75c
Affective attitudes	3	0.74	151	For you, drinking less than 1 cup of sugary drinks each day would be: Enjoyable/unenjoyable Pleasant/unpleasant Exciting/unexciting	0.87c
Instrument-al attitudes	3	0.80	153	For you, drinking less than 1 cup of sugary drinks each day would be Healthy/unhealthy Wise/unwise Harmful/beneficial	0.86c
Subjective norms	3	0.62	152	Most people who are important to you want you to drink less than 1 cup of sugary drinks each day. Agree/disagree For most people whose opinions you value, how would they feel about you drinking less than 1 cup of sugary drinks each day? Disapprove/approve Most people who are important to you will drink less than 1 cup of sugary drinks each day. Untrue/true	0.81c

Note: responses to all questions are on a 7-point Likert scale.

^aThe single-item indicator question is bolded. The response scale is italicised.

^bPearson’s Correlation comparing single-item indicator to multi-item scale using baseline data.

^cAll correlations between the single-item indicators and multi-item scales are significant at p < 0.001.