Online questionnaire

The online questionnaire included a number of published self-report measures that collected information about perceived stress, coping responses, eating behaviours, self-efficacy, physical exercise and social support, along with a demographic questionnaire. These were:

1. 10-item Perceived Stress Scale (PSS-10; Cohen et al. 1983) 2. Ways of Coping Questionnaire (Folkman & Lazarus 1988) 3. Dutch Eating Behaviour Questionnaire (DEBQ; van Strien 2010)

4. Multidimensional Scale of Perceived Social Support (MSPSS; Zimet et al. 1988) 5. General Self‐Efficacy Scale (GSE; Schwarzer & Jerusalem 1995)

6. Nutrition Self‐Efficacy Scale and Exercise Self‐Efficacy Scale (Schwarzer & Renner 2000) 7. International Physical Activity Questionnaire (IPAQ 2001).

The above measures were chosen as these have been assessed, and have demonstrated adequate reliability and validity, they are not too long or complex, and are culturally as well as developmentally appropriate. (These measures are described in Sections 3.1.6.3.1 to 3.1.6.3.8)

The online questionnaire also contained a demographic questionnaire and a background information questionnaire specifically designed for this study. The demographic questionnaire included questions about anthropometric measurements, e.g. current height (in cm) and weight (in kg) needed to calculate each participant’s BMI (kg/m²), in order to provide an objective weight measure, as well as current waist circumference (in cm), and other personal information, e.g. gender and access to Internet at home. (The two measures used to determine overweight and obesity status, i.e. BMI and waist circumference, will be described in further detail in Sections 3.1.6.3.1 and 3.1.6.3.2, respectively.) The background information questionnaire collected information such as the availability of support from family and friends with regards to improving food choice as well as about smoking and drinking habits.

Since the data collection tool is long, the order in which the questions were placed reflects the degree of importance of the questions to the study. Hence, questions about perceived stress, coping responses, eating behaviours and demographic data including weight status are placed at the beginning of the questionnaire. This was done so that in the eventuality of premature termination, i.e. adolescents deciding not to fill in the entire questionnaire, the chance of collecting data about the main variables under investigation would be maximised.

Prior to preparing the online questionnaire, permission was sought as to whether the Ways of Coping Questionnaire (Folkman & Lazarus 1988) and the DEBQ (van Strien 2010) could be changed to an online format and hosted on a secure website with access limited to an agreed number of participants. This was necessary since both of these tools are copyrighted and not free to use for research purposes.

The online form of the questionnaire was produced using LimeSurvey, an open source survey application, and was hosted on the Plymouth University server. All data collected in the study were saved on this secure server with back-up copies saved on the researcher’s private

The questionnaire consisted of both multiple-choice and open-ended questions. For multiple- choice questions, radio buttons were associated with all possible responses, whilst for open- ended text type questions, comment boxes were created. All the items, belonging to a particular measure used in the study, were presented on the same screen page as would be the case in paper-and-pencil questionnaires. Rules were set, using LimeSurvey, so that participants would:

• require a token (unique access code) to access the questionnaire,

• not be able to progress to the next question until the current question was answered to avoid any missing data in submitted questionnaires,

• be able to save partially finished questionnaires and continue from where they left off on another occasion (by clicking on a ‘Resume Later’ button on the bottom left-hand- side of each screen; Figure 5), as well as,

• not be able to use the token (unique access code) again once the survey is completed.

The use of tokens (unique access codes) eliminated the possibility of the same participant submitting multiple completed questionnaires as well as the receipt of unsolicited responses, i.e. the participation of individuals who were not recruited in the study. Using tokens/codes is a recommended solution to avoid these potential sampling issues (Wright 2005).

The tokens (unique access codes) set for this study were 7 character alphanumeric codes, containing both uppercase and lowercase letters (e.g. 15Tv822), which were unique to each participant and without which the study questionnaire could not be accessed. The tokens for this study were randomly generated using an online strong password generator (http://strongpasswordgenerator.com).

Figure 5: Data entry screen shot depicting the ‘Resume Later’, ‘Previous’, ‘Next’, and ‘Exit and Clear Survey’ buttons

The initial screen of the online questionnaire provided the participants with study details including the aims of the research and an assurance of confidentiality. A space to enter the token, which was necessary to access the questionnaire, was also provided on this initial screen.

As with a paper-and-pencil questionnaire, back-tracking and changing previous answers in the online questionnaire was possible by clicking the ‘Previous’ and ‘Next’ buttons on the bottom of the screen (Figure 5). An ‘Exit and Clear Survey’ button, at the bottom right-hand-side of each screen (Figure 5), enabled respondents to discontinue their participation in the survey at any point without any of their answers being saved. Respondents could also keep track of how many items still needed completion by means of a progress bar (expressed in percentages) at the top of each screen (Figure 6). The inclusion of a progress bar was deemed important because it provides the opportunity for respondents to estimate the length of a questionnaire

and the time required for completion, therefore decreasing the likelihood of abandonment/premature termination (Lumsden 2007; Lumsden & Morgan 2005).

Figure 6: Data entry screen shot depicting progress bar at the top of the screen