The Impact of Price Promotions on Purchases of Confectionery and Snacks: a Randomised Controlled Trial in an Experimental Online Supermarket Study
Phase: NA
Conditions: Healthy Diet
Sponsor: University of Oxford

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Study Title:  The impact of price promotions on purchases of confectionery and snacks: a randomised 
controlled trial in an experimental online supermarket study 
Internal Reference Number / Short title:  
Med IDREC Ref: R65010/RE005 
Date and Version No: 24th September 2021, Version 2.0 
 
Chief Investigator: 
Dr Carmen Piernas-Sanchez1 
carmen.piernas-sanchez@phc.ox.ac.uk, 01865 289284 
Nuffield Department of Primary Care Health Sciences, University of 
Oxford 
 
Investigators:  
 
Dr Rachel Pechey1 
Dr Lauren Bandy1 
Georgina Harmer1 
Professor Susan Jebb1 
1Nuffield Department of Primary Care Health Sciences, University of 
Oxford 
Sponsor:  
University of Oxford 
Funder: 
National Institute for Health Research (NIHR) Applied Research 
Collaborations (ARC Oxford). 
Chief Investigator Signature:  
 
 
 
Conflicts of interest 
None declared. 
Confidentiality Statement 
This document contains confidential information that must not be disclosed to anyone other than the 
authorised individuals from the University of Oxford, the Investigator Team and members of the Medical 
Sciences Interdisciplinary Research Ethics Committee (Medical Sciences IDREC), unless authorised to do 
so. 
 

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TABLE OF CONTENTS 
 
1. 
SYNOPSIS ..........................................................................................................................................4 
2. 
ABBREVIATIONS ................................................................................................................................5 
3. 
BACKGROUND AND RATIONALE ........................................................................................................6 
4. 
OBJECTIVES AND OUTCOME MEASURES ...........................................................................................7 
5. 
STUDY DESIGN ..................................................................................................................................8 
6. 
INTERVENTION ..................................................................................................................................8 
7. 
PARTICIPANT IDENTIFICATION AND RECRUITMENT ...........................................................................9 
7.1. 
Study Participants ......................................................................................................................9 
7.2. 
Inclusion Criteria .......................................................................................................................9 
7.3. 
Exclusion Criteria .......................................................................................................................9 
8. 
STUDY PROCEDURES ....................................................................................................................... 10 
8.1. 
Recruitment ............................................................................................................................ 10 
8.2. 
Screening and Eligibility Assessment ........................................................................................ 10 
8.3. 
Informed Consent .................................................................................................................... 10 
8.4. 
Randomisation ........................................................................................................................ 10 
8.5. 
Blinding ................................................................................................................................... 10 
8.6. 
Baseline Assessments .............................................................................................................. 11 
8.7. 
Follow-up ................................................................................................................................ 11 
8.8. 
Discontinuation/Withdrawal of Participants from Study .......................................................... 11 
8.9. 
Definition of End of Study ........................................................................................................ 11 
9. 
STATISTICS AND ANALYSIS ............................................................................................................... 11 
9.1. 
The Number of Participants ..................................................................................................... 11 
9.2. 
Analysis of Outcome Measures ................................................................................................ 11 
10. 
DATA MANAGEMENT .................................................................................................................. 12 
10.1. 
Access to Data ..................................................................................................................... 12 
10.2. 
Data Handling and Record Keeping ...................................................................................... 12 
11. 
QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES ...................................................... 12 
12. 
ETHICAL AND REGULATORY CONSIDERATIONS ............................................................................ 12 
12.1. 
Declaration of Helsinki ......................................................................................................... 12 
12.2. 
Approvals ............................................................................................................................ 13 
12.3. 
Participant Confidentiality ................................................................................................... 13 
12.4. 
Expenses and Benefits ......................................................................................................... 13 

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12.5. 
Other Ethical Considerations................................................................................................ 13 
13. 
FINANCE AND INSURANCE ........................................................................................................... 14 
13.1. 
Funding ............................................................................................................................... 14 
13.2. 
Insurance ............................................................................................................................. 14 
14. 
PUBLICATION POLICY .................................................................................................................. 14 
15. 
REFERENCES ................................................................................................................................ 15 
16. 
APPENDIX A:  STUDY FLOW CHART .............................................................................................. 17 
17. 
APPENDIX B:  SCHEDULE OF STUDY PROCEDURES ....................................................................... 18 
18. 
APPENDIX C:  AMENDMENT HISTORY .......................................................................................... 22 
 
 
 

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1. SYNOPSIS 
 
Study Title 
Impact of price promotions on purchases of confectionery and snacks: a 
randomised controlled trial in an experimental online supermarket study 
Internal ref. no.  
N/A 
Study Design 
Randomised controlled trial 
Study Participants 
Healthy volunteers from the UK 
Planned Sample Size 
500 
Planned Study Period 
June – December 2021 
 
Objectives 
Outcome Measures 
Primary 
 
To investigate the effect of 
promotions on the total number of 
calories selected  
 
Difference in the absolute energy 
(kcal) of the final basket between 
the two groups 
Secondary 
 
To investigate the effect of 
promotions on the nutritional content 
of the items selected overall, and 
across the individual target food 
categories 
 
 
 
 
 
 
 
To explore the impact of removing 
promotions by socioeconomic status 
 
Difference in the absolute sugar (g, 
kcal, %E), salt (g), and saturated fat 
(g, kcal, %E) of the final basket 
between the two  groups 
 
Difference in the absolute energy 
(kcal), sugar (g, kcal, %E), salt (g), 
and saturated fat (g, kcal, %E) 
between the two groups across 
the individual target food 
categories 
 
Analyses of the primary and 
secondary outcomes specified 
above by gender, age group, ethnic 
group (White vs Non-White), BMI 
stratified into <30 and ≥30kg/m2 
groups, education level (lower vs. 
higher), and household income 
(lower vs. higher) 
Exploratory  
To investigate the acceptability of the 
intervention  
Rating scores and open-ended 
answers from the follow-up 
questionnaire  
 

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2. ABBREVIATIONS 
 
 
 
CI 
Chief Investigator 
CLARHC 
Collaboration for Leadership in Applied Health Research and Care 
IDREC 
Interdisciplinary Research Ethics Committee 
SAP 
Statistical Analysis Plan  
SFA 
Saturated Fat 
TPR 
Temporary Price Reduction  

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3. BACKGROUND AND RATIONALE 
 
As a nation we eat more energy, free sugars, saturated fat and salt than recommended for good health 
(1). These nutrients contribute to the burden of major chronic diseases, including cardiovascular disease 
and diabetes, principally through effects on blood cholesterol, blood pressure, insulin sensitivity or body 
weight (2-6). In addition, persistent inequalities in dietary intake underpin inequalities in long-term 
health outcomes. Despite decades of health promotion, dietary change is slow. Growing evidence 
suggests people need more than general knowledge about the healthfulness of foods to change 
behaviour (7-11).  
 
Food purchasing is a key antecedent of food consumption and interventions to change food purchasing 
habits may be more impactful than interventions intended to change consumption at the moment of 
eating. Supermarkets account for the majority of the weekly expenditure on food and drinks, estimated 
to be around 87% of all UK retail grocery sales (12). Impactful, scalable and sustainable approaches 
within supermarkets are particularly needed in order to shift population-level intakes to be closer to the 
recommendations for calories, sugar, salt and saturated fat. 
 
Previous systematic reviews of supermarket interventions have identified effective strategies to support 
dietary change (13-23). Evidence is generally stronger for economic (e.g. price interventions or price 
promotions), positioning and availability interventions. However, many of the interventions described in 
the literature are multi-component, and there is a challenge in attributing their effectiveness to any 
single strategy. In the 2020 Obesity Plan, the government in England laid out plans to introduce 
legislation to restrict the promotion of high fat salt sugar (HFSS) foods, by restricting volume promotions 
such as ‘Buy One Get One Free’. This is based on observational evidence of purchasing habits. Specific 
evidence of the impact of removing promotions is of interest to policymakers and could help in shaping 
effective but proportionate policies. 
 
Online supermarkets offer unique opportunities to deliver and support complex nutrition interventions 
that can often be tested and scaled up more rapidly and feasibly using digital technology than in-store 
interventions. There is some evidence that baseline purchases made online tend to be healthier than 
purchases in physical stores, but less is known about the effectiveness of interventions delivered online 
to change behaviour. 
 
The purpose of this project is to test the effectiveness of the removal of price promotions on 
confectionery and snacks on the energy, sugar and saturated fat content of items selected while 
shopping online in a representative sample of UK adults. The proposed intervention can be easily 
implemented, and could reach large numbers of people, meaning that if it is effective it could have a 
significant population impact and be very cost-effective, even if the effect size is smaller than more 
intensive interventions. 
 

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4. OBJECTIVES AND OUTCOME MEASURES 
 
 
Objectives 
Outcome Measures 
Primary 
 
To investigate the effect of 
promotions on the total number of 
calories selected  
Difference in the absolute energy 
(kcal) of the final basket between 
the two groups 
Secondary 
 
To investigate the effect of 
promotions on the nutritional content 
of the items selected overall, and 
across the individual target food 
categories 
 
 
 
 
 
 
 
To explore the impact of removing 
promotions by socioeconomic status 
 
Difference in the absolute sugar (g, 
kcal, %E), salt (g), and saturated fat 
(g, kcal, %E) of the final basket 
between the two  groups 
 
Difference in the absolute energy 
(kcal), sugar (g, kcal, %E), salt (g), 
and saturated fat (g, kcal, %E) 
between the two groups across 
the individual target food 
categories 
 
Analyses of the primary and 
secondary outcomes specified 
above by gender, age group, ethnic 
group (White vs Non-White), BMI 
stratified into <30 and ≥30kg/m2 
groups, education level (lower vs. 
higher), and household income 
(lower vs. higher) 
Exploratory  
To investigate the acceptability of the 
intervention  
Rating scores and open-ended 
answers from the follow-up 
questionnaire  

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5. STUDY DESIGN 
This is a randomised controlled trial with a parallel design. We will use an experimental online shopping 
platform to mimic the experience of online grocery shopping. Each participant will be randomised 1:1 to 
one of two groups and will participate in an online shopping task for about 10 minutes during which they 
will be exposed to a selection of products including promotions or with no promotions. We will collect 
and analyse data from the online platform on food selection during the task. 
6. INTERVENTION 
This study uses a bespoke virtual online supermarket shopping (OLS) platform, hosted by The University 
of Oxford, which emulates a real online supermarket for research purposes relating to food purchasing 
interventions (www.woodssupermarket.co.uk). The site is populated with approximately 23,000 current 
supermarket products drawn from foodDB (April 2019), a weekly updated database of food and drinks 
available for purchase in six UK online supermarkets (24).  
Participants will be asked to imagine they are buying snacks for a night in with 4 friends, with a maximum 
limit of £10. They will be asked to select products from the following categories, which are aligned and 
named in the way items are presented in the store:  
- 
Confectionery  
- 
Biscuits and crackers 
- 
Crisps, nuts and snacking fruit  
- 
Cakes and tarts 
 
The shopping task is estimated to take participants 10 minutes to complete. Participants will only be 
asked to complete the shopping task once. Participants will be provided with the following instructions:  
“We would like you to do some online grocery shopping on a supermarket website. This is not a real 
supermarket, and you will not be asked to spend your own money.   
We would like you to imagine you are buying snacks for a night in with 4 friends, up to a limit of £10. You 
should select products from the following categories:  
- 
Confectionery  
- 
Biscuits and crackers 
- 
Crisps, nuts and snacking fruit 
- 
Cakes and tarts 
We would ask you not to select any additional items from your usual shopping list.  
 
When doing your shopping, try to imagine you are doing your own grocery shopping and choose foods 
that you and your friends would eat. You should choose the things you normally buy or wouldn’t mind 
eating. 
To make sure you get your reward, please make sure you buy at least £5 worth of products within the 
suggested food categories” 
Participants will be randomly allocated to one of the two following groups when shopping online: 

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1. Promotions removed: No promotions present on any of the products within the target food 
categories [confectionery; biscuits and crackers; crisps, nuts and snacking fruit; cakes and tarts] 
offered to participants when searching for products. 
2. Promotions included: Participants in this group will see a version of the website which will 
reproduce the types and frequency of promotions that can be found in any online supermarket, 
for example multi-buy offers and temporary price reductions will be applied to a pre-determined 
percentage of food products within the target categories [confectionery; biscuits and crackers; 
crisps, nuts and snacking fruit; cakes and tarts]. Promotions will be applied to match the current 
levels and types of promotions on the website of the largest UK retailer present in a specific 
week, shortly before the study launch.   
7. PARTICIPANT IDENTIFICATION AND RECRUITMENT 
7.1. Study Participants 
Eligible participants will be UK adults who are responsible for a substantial proportion of their household 
grocery shopping, able to read and understand the instructions provided and able to provide online 
consent to take part in the study. Participants will be required to have access to a computer and the 
internet. 
People who are following a vegan, gluten-free, dairy-free or sugar-free diet will not be eligible to 
participate to minimise the risk of unbalancing the groups with people choosing from a restricted 
selection of products.  
7.2. Inclusion Criteria 
 
UK adults, aged ≥18 years. 
 
Able to speak and read English. 
 
Willing and able to give informed consent for participation in the study. 
 
Having access to a computer and Internet. 
7.3. Exclusion Criteria 
The participant may not enter the study if ANY of the following apply: 
 
They are following a dairy-free or sugar-free diet.

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8. STUDY PROCEDURES 
8.1. Recruitment 
Participants will be recruited from the volunteer panel Prolific Academic (https://www.prolific.co).   
8.2. Screening and Eligibility Assessment 
Panel members will be sent an email introducing the study and including a link to the participant 
information sheet. Panel members who are interested in taking part in the study will be asked to click on 
a web-link from the email, which will take them to the study registration website (on Qualtrics). At this 
registration website, they will be asked screening questions indicating their responsibility for shopping, if 
they have any dietary restriction, if they regularly buy products from the target categories for their 
household, and to confirm their age and country of residence. They will also be able to re-read the 
detailed participant information before consenting to participate. 
8.3. Informed Consent 
After reading the detailed participant information sheet and answering screening questions to confirm 
they meet the inclusion/exclusion criteria; and if they are happy to proceed, participants will be asked to 
give consent electronically to take part in the study. 
Written electronic versions of the Participant Information and Informed Consent will be presented to the 
participants detailing no less than: the exact nature of the study, what it will involve for the participant 
and the implications and constraints of the protocol. It will be clearly stated that the participant is free to 
withdraw from the study at any time for any reason and with no obligation to give the reason for 
withdrawal. The participant will be allowed as much time as wished to consider the information. 
Electronic Informed Consent will then be obtained by means of clicking on a tick box. 
8.4. Randomisation 
Randomisation will be performed by the survey platform Qualtrics via computerised random number 
generation on a 1:1 basis with random block sizes and participants will be directed to a website that 
introduces an online shopping task. Allocation concealment is achieved, as participants are recruited 
from independent research panels and are being directed by automatic randomisation in the survey 
platform. Details of the intervention are described in Section 6. 
8.5. Blinding 
Investigators will be blinded to intervention allocation and will not be able to manipulate any study 
parameter following the initial study set up, as all study procedures are taking part in the online 
platform. The outcome assessment is blinded, as it happens automatically in the online platform. The 
statistician who will analyse the data will be blinded to intervention allocation. Participants will only be 
aware of the trial arm that they are exposed to and will be unaware of the other trial arm. 

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8.6. Baseline Assessments 
Following consent and completion of the shopping task, participants will complete a baseline 
questionnaire on demographic, shopping, and health data (Appendix B). 
8.7. Follow-up 
Participants will complete a short post-intervention survey (Appendix B) about the acceptability of the 
intervention in the online shopping task and their usual shopping behaviours. 
8.8. Discontinuation/Withdrawal of Participants from Study 
 
Each participant has the right to withdraw from the study at any time. Participants will not be replaced 
as we will recruit sufficient sample size to allow for non-completion rate. Withdrawal from the study, 
based on the pre-defined completion criteria (section 9.2), will result in exclusion of the data for that 
participant from analysis. 
8.9. Definition of End of Study 
The end of study is the completion of the baseline questionnaire and post-intervention survey following 
the shopping task.  
9. STATISTICS AND ANALYSIS 
9.1. The Number of Participants 
There are no previously reported standard deviations of the mean difference from similar trials (e.g. 
where a one-off shop is done) to guide the estimation of the effect size and standard deviation, and, 
thus, the calculation of the sample size. However, the study by Brimblecombe et al. (25) implemented a 
complex intervention within real supermarkets in Australia where promotions on high sugar products 
were removed, including confectionery and sugary drinks. This study found a total reduction of -22% in 
sales (g/MJ) in confectionery, a difference of -4.5% (SD 15) compared to control; and a reduction of -8% 
in sugar-sweetened soft drinks, a difference of -13% compared to control.  
A total sample of 500 participants (250 in each group) would be needed to detect a minimum effect size 
of -4.5% in total kcal from the target categories, with 90% power, 5% alpha and 10% attrition.   
9.2. Analysis of Outcome Measures 
 
Completion of the task will be defined as spending at least £5 on products from the target categories.  
Primary Analysis 
Linear regression models will compare the total energy (kcal) purchased in the two groups. Any baseline 
variables (e.g. demographic characteristics) which appear to have been imbalanced between groups will 
be adjusted in the model.  

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Secondary Analysis 
Linear regression models will compare the (i) total sugar (g, kcal, %E), (ii) total salt (g, kcal, %E) and (iii) 
total SFA (g, kcal, %E) purchased in the two groups. 
Secondary analyses will also compare differences in total energy (kcal), total sugar (g, kcal, %E), total salt 
(g, kcal, %E) and total SFA (g, kcal, %E) across the individual target categories.  
We will also conduct secondary analyses of the primary and secondary outcomes specified above by 
gender, age group, ethnic group (White vs Non-White), BMI stratified into <30 and ≥30kg/m2 groups, 
education level (lower vs. higher), and household income (lower vs. higher) provided we have sufficient 
numbers within each subgroup (n30).  
Descriptive analysis 
The exploratory outcome measures will be discussed descriptively.  
A Statistical Analysis Plan will be finalised before conducting the statistical analysis. 
10. DATA MANAGEMENT 
10.1. 
Access to Data 
Direct access will be granted to authorised representatives from the University of Oxford for monitoring 
and/or audit of the study to ensure compliance with regulations.  
10.2. 
Data Handling and Record Keeping 
All study data will be captured in a password protected secure database. The participants will be 
identified by a unique study specific number and/or code in any database.  Personal data will not be 
collected in this study. Research data and records will be retained for at least three years after 
publication or public release of the work of the research and reviewed thereafter. 
11. QUALITY CONTROL AND QUALITY ASSURANCE PROCEDURES 
The study will be conducted in accordance with the current approved protocol, relevant regulations and 
standard operating procedures.  
12. ETHICAL AND REGULATORY CONSIDERATIONS 
12.1. 
Declaration of Helsinki 
The Investigator will ensure that this study is conducted in accordance with the principles of the 
Declaration of Helsinki. 
 

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12.2. 
Approvals 
The protocol, informed consent form, participant information sheet and any proposed advertising 
material will be submitted to the ethical committee for approval. 
The Investigator will submit and, where necessary, obtain approval from the above parties for all 
substantial amendments to the original approved documents. 
12.3. 
Participant Confidentiality 
All data collected by participants will be anonymous. The participants will be identified only a participant 
ID number on all study documents and any electronic database.  All documents will be stored securely 
requiring password-protected access and will be only accessible by study staff and authorised personnel.  
Privacy and confidentiality of data is particularly hard to manage in Internet-based research because as 
researchers we are not in control of online communication networks, leading to the risk of third-party 
interceptions.  We will encourage the use of a secure link at the consent stage. Participants will be 
informed that we will not collect their IP addresses. As the data will be anonymised, it does not 
constitute personal data and the duties and obligations of the Data Protection Act do not apply. The 
research agencies will only share with the researchers a participant ID and no personal data. 
12.4. 
Expenses and Benefits 
Participants will be rewarded with £25p for the screening survey and £1.5 for completing the shopping 
task and survey. 
12.5. 
Other Ethical Considerations 
Internet based research issues 
a) 
Authentication 
The research agency who will recruit participants uses a number of mechanisms to authenticate 
responders such as checking for duplicate respondents by evaluating variables such as email address, 
matches across several demographic data, and device-related data through use of digital fingerprint 
technology.  
b) 
Participant rights 
Participants will be free to withdraw themselves and their data at any point in the research. During the 
shopping task, clicking on a clearly displayed “exit here” button will lead participants to a quick debrief 
page that will give them the option to confirm that they do not wish their data to be retained for the 
study purposes. Participants will be clearly informed before giving consent that anonymity makes 
withdrawal following completion of the study difficult. 
 
 
 

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13. FINANCE AND INSURANCE 
13.1. 
Funding 
The study is funded by the National Institute for Health Research (NIHR) Applied Research Collaborations 
(ARC Oxford). 
13.2. 
Insurance 
This is a simple online task and we cannot foresee any unintended or adverse effects due to 
participation. The University of Oxford maintains Public Liability and Professional Liability insurance that 
will operate in this respect. 
14. PUBLICATION POLICY 
The Investigators will be involved in reviewing drafts of the manuscripts, abstracts, press releases and 
any other publications arising from the study. Authors will acknowledge that the study was funded by 
the NIHR Oxford ARC. Authorship will be determined in accordance with the ICMJE guidelines and other 
contributors will be acknowledged. As we will not store the participants’ contact details, we will not be 
able to disseminate the results directly to study participants. We will follow our dissemination plan to 
engage with public health agencies, the industry, the media, and the public. 
 

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16. APPENDIX A:  STUDY FLOW CHART 
 
 
 

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17. APPENDIX B:  SCHEDULE OF STUDY PROCEDURES 
RECRUITMENT TEXT 
The content of the recruitment text will be consistent with other emails sent to panel members but will 
contain the following text: 
Survey topic: Health, Survey length: 10 minutes, Reward: £ xxx  
Hi [Name], 
We have a new survey available for you. By qualifying and completing this task, you will receive £xxx.  
This study is being carried out by the University of Oxford. The study aims to investigate ways of helping 
people make healthier choices when they shop in an online supermarket. The purpose of this study is to 
explore how people shop for confectionery and snacks in an online supermarket. It will involve 
completing an online shopping study which should take no more than 10 minutes.  
Before undertaking the task, you will be asked to read some detailed participant information, to confirm 
you are eligible, and confirm your consent to participate.  
For further information and to take part go to [link to survey page (PIS and consent) and shopping 
website]. 
 
SCREENING QUESTIONS (Pre-shopping) 
1. Age  
 
Under 18 years old 
 
18 years old or over 
 
2. Do you currently reside in the UK? 
 
Yes 
 
No  
 
3. Are you fluent in English? 
 
Yes 
 
No  
 
4. Do you have any dietary restrictions? 
 
Vegan 
 
Gluten-free 
 
Sugar-free 
 
Dairy/lactose-free 
 
None 
 
Rather not say 
 
5. Are you the main (or shared) grocery shopper for the food that your household eats? 

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 
Yes 
 
No 
 
BASELINE MEASURES (Socio-demographic, shopping and health measures) 
1. Demographic characteristics 
 
Gender  
o Male 
o Female 
o Other 
o Prefer not to say 
 
Age (years) 
o Free text (range of 18-99) 
o Prefer not to say 
 
Ethnicity (UK Census simplified) 
o White 
o Black 
o Asian 
o Mixed 
o Other 
o Prefer not to say 
 
Weight and height (in units chosen by participant). 
 
2. Household income (total household income before tax) 
 
Below £15.5K 
 
Between £15.5K up to and including £25K 
 
Between £25K and £39K 
 
£40K or above 
 
3. Household size – “How many people live at your house, including you? 
4. Highest educational level) - “What is the highest education qualification you have achieved?” 
(categories based on UK census categories) 
 
None 
 
Up to 4 GCSE's (Including 1-4 O Levels/CSE/GCSEs (any grades), Foundation Diploma, NVQ level 
1, Foundation GNVQ or equivalents) 
 
5 or more GCSE's or 1 A-level (Including 5+ GCSEs (Grades A*-C),1 A Level/ 2-3 AS Levels, NVQ 
level 2, Intermediate GNVQ, City and Guilds Craft, BTEC First/General Diploma, RSA Diploma, 
Apprenticeship or equivalents) 
 
2 or more A-levels (Including 2+ A Levels, 4+ AS Levels, NVQ Level 3, Advanced GNVQ, City and 
Guilds Advanced Craft, ONC, OND, BTEC National, RSA Advanced Diploma or equivalents) 
 
Bachelor's degree (Including BA, BSc, NVQ Level 4-5, HNC, HND, RSA Higher Diploma, BTEC 
Higher level or equivalents) 

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 
Post-Graduate degree or qualification (Including Higher Degrees e.g. MA, PhD, PGCE, 
Professional qualifications e.g. teaching, nursing, accountancy or equivalents) 
 
5. Regular shopping  
“On average, how much do you spend on supermarket shopping per week?” (answer in £) 
6. Online shopping experience 
“How often, on average over the past year, have you shopped online for food or groceries to be 
delivered to you (e.g. Tesco.com, Ocado.com, mysupermarket.co.uk)?“ 
 
Never or not in the last year 
 
1-3 times in the last year 
 
4-11 times in the last year 
 
1-3 per month 
 
Once per week or more often. 
 
 
POST-SHOPPING TASK PARTICIPANT SURVEY  
 
 
1.  “Did you see any promotions in the online supermarket you used in the shopping task today?”  
 
“Yes/No/Don’t know” 
1A. “Do you usually buy products on promotion when you do your usual shopping?” 
 
Strongly agree 
 
Somewhat agree 
 
Indifferent 
 
Somewhat disagree 
 
Strongly disagree 
 
1B. “Out of the two promotional strategies, product price reductions (e.g. save £1, reduced to 99p) 
or multi-buy offers (e.g. 3 for 2, buy-one-get-one-free), which is more likely to influence what you 
buy?” 
 
Price reductions 
 
Multi-buy offers 
 
 
 
 
2.  “When making a choice of foods or drinks to buy, what are the top 3 things that affect your 
decision?” 

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 
Price 
 
Appearance 
 
Taste (preference) 
 
Habits 
 
Healthiness 
 
Convenience (to prepare or to consume) 
 
Special offers 
 
Organic 
 
Special diet e.g. gluten free, nut free 
 
Other (e.g. animal welfare, locally produced, packaging) 
 
3. “The UK government is considering a policy to ban all promotions on high fat salt sugar products 
in supermarkets (both in-stores and online). To what extent would you support or oppose this 
policy? 
 
Strongly support 
 
Support 
 
Somewhat support 
 
Neither support nor oppose 
 
Somewhat oppose 
 
Oppose 
 
Strongly oppose 
 
3A. “For what reason did you give this answer?” 
[FREE TEXT ANSWER] 
4. “Is there anything else you’d like to tell us about your experience with this shopping task today?” 
(Please do NOT include your name here). 
[FREE TEXT ANSWER] 
 
 

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18. APPENDIX C:  AMENDMENT HISTORY 
 
Amendment 
No. 
Protocol 
Version 
No. 
Date issued Author(s) 
of changes 
Details of Changes made 
1.0 
2.0 
24/09/2021 Carmen 
Piernas 
-Added Lauren Bandy to the study team 
- Clarified secondary outcomes in the 
boxes in pages 4 and 7  
- Removed fizzy drinks from the target 
categories 
- Changed £15 to £10 as the maximum 
amount of money to be spent in the 
shopping experiment 
- Clarified the estimated payment to be 
received (25p for screening survey and 
£1.5 from Prolific recruitment)