Validity and Reliability Testing of a Short Questionnaire Developed to Assess Consumers’ Use, Understanding and Perception of Food Labels

Home , Validity (statistics)

ORIGINAL ARTICLE Validity and reliability testing of a short questionnaire developed to assess consumers’ use, understanding and perception of food labels

D Mackison1, WL Wrieden2 and AS Anderson1

1Centre for Public Health Nutrition Research, Division of Clinical and Population Sciences and Education (CPSE), University of Dundee, Ninewells Hospital and Medical School, Dundee, UK and 2School of Pharmacy and Life Sciences, The Robert Gordon University, Aberdeen, UK

Background: Food labels may have an important function in communicating nutrition information and have considerable potential to influence food choice and dietary behaviour. Objectives: To assess the validity and reliability of a short (self-complete) questionnaire designed to measure consumers’ use and understanding of food labels. Methods: Questionnaire content was determined by gaps highlighted in a literature review of food labelling. Nineteen questions (49 items) assessing frequency of label reading perceived importance of food labels, regularity of dining out, desire to have nutrition information at specific catering outlets and ability to perform nutrition information tasks were formulated and presented on four pages of A4. With the exception of two open-ended questions, all items were presented as closed (field box) structures. Content validity, face validity, item analysis, repeat and internal reliability were assessed. Results: Nutrition experts (26) completed detailed content validity assessment, resulting in high scores for appropriateness, importance and phrasing of questions, although grammar and terminology changes were required. Face validity indicated that the questionnaire was quick to complete (o15 min), easy to follow and comprehensible. Cronbach’s alpha scores (internal reliability) for questions with multiple sections ranged from 0.72 to 0.91, indicating good internal consistency. Repeat reliability testing showed Spearman’s correlation coefficients ranging from 0.51 to 0.97 (all Po0.001) showing high temporal stability. Item Difficulty analysis indicated that questions (Section C only) were at an appropriate level (with P between 20 and 80% for all items). Item discrimination analysis ranged from r ¼ 0.43 to 0.70, highlighting that items were suitable for inclusion. Conclusions: This questionnaire is a suitable tool for assessing consumers’ use, understanding and perception of food labels. European Journal of Clinical Nutrition (2010) 64, 210–217; doi:10.1038/ejcn.2009.126; published online 11 November 2009

Keywords: food labelling; labels; validity; reliability; questionnaire development

Introduction Encouragingly, most consumers claim to read food labels often or sometimes (Cowburn and Stockley, 2005; European Food labels are recognized as having a pivotal function in Heart Network, 2003). Available literature, however, suggests communicating nutrition information to consumers and are that while consumers claim to understand the information considered to have the potential to influence food choice they are reading (National Institute of Nutrition, 1999; and dietary behaviour. For the consumer to make healthy Stuart et al., 2004; Food Standards Agency, 2007), their actual food choices, they must be able to locate, read, interpret and understanding is selective (European Heart Network, 2003; understand the information presented on food labels. Cowburn and Stockley, 2005). Consumers display little difficulty judging the nutrient levels of products (Food Correspondence: D Mackison, Division of Clinical and Population Sciences Standards Agency, 2006), yet struggle when asked to perform and Education (CPSE), Centre for Public Health Nutrition Research, University arithmetical calculations and comparisons of different sizes of Dundee, Ninewells Hospital and Medical School, Dundee, DD1 9SY, UK. and types of products (Levy and Fein, 1998; Rothman et al., E-mail: [email protected] Received 21 January 2009; revised 16 July 2009; accepted 20 July 2009; 2006). Creating food label information that is easily inter- published online 11 November 2009 preted by consumers requires knowledge of the specific label Short questionnaire assessing food label use and understanding D Mackison et al 211 attributes that consumers read and use. Energy and fat consumers’ desire to have nutrition information available in information are the most commonly read nutrient by the catering establishments. To date, there has been limited consumer (Black and Rayner, 1992; Institute of Grocery research conducted on the British consumers’ views on the Distribution, 1998; Kessler and Wunderlich, 1999; Marietta application of nutrition style information in catering outlets. et al., 1999; Neuhouser et al., 1999; Higginson et al., 2002; The aim of this study was to develop a valid and reliable Krukowski et al., 2006; Mannell et al., 2006); however, we short questionnaire to assess consumers’ use, understanding know little about the consumer’s interpretation of this and perception of food labels in both the retail and catering information and how this influences their food purchase environment. decisions (Grunert and Wills, 2007). In a bid to standardize and ease the delivery of nutrition information to the consumer, many countries have Methods adopted mandatory nutrition information on food labels (for example United States, Australia and Canada) (Hawkes, Questionnaire development 2004). If successful, the European Union’s recent proposal for Key areas were identified after a literature review on food a Regulation on the provision of food information to labelling and a draft questionnaire was devised. Five sections consumers (the consolidation and update of the general (A–E) were identified: food-labelling legislation (Council Directive 2000/13/EC of a. Frequency of reading specific attributes on food labels, in the European Parliament and of the Council of 20 March which food labels are read, and importance of food labels 2000, 2000) and the nutrition-labelling legislation (Council b. Frequency of using, views on quantity and perceived Directive 90/496/EEC of 24 September on nutrition labelling importance of nutrition information on food labels for foodstuffs, 1990)) would introduce mandatory nutrition c. Objective assessment of nutrition label tasks labelling on the ‘principal field of vision’ (front of pack) on d. Frequency of using specific catering establishments and all products throughout Member States (EU, 2008). During desire to see nutrition and additional information avail- the consultation and implementation phases of this Regula- able in specific catering establishments tion, increased consumer awareness of nutrition information e. Demographic information on food labels is anticipated as a direct result of media coverage and as labelling changes become prevalent The instrument was intended to be completed indepen- throughout stores. The introduction of a new standardized dently by adults aged 18 years of age and older, and it was nutrition-labelling format provides a valuable opportunity essential that the questionnaire was short in length (four for education interventions focused on food labelling to take sides of A4 paper), quick to complete (o20 min), easy to centre stage. However, before public health practitioners can follow, comprehensible and contained short questions (with tackle educating consumers on the new food-labelling language suitable for the target group). Questionnaire read- formats, it is imperative that we gain a better understanding ability was assessed using the Flesch Reading Ease Score of the consumer’s views on food labels. More information is available on computer software (Microsoft Word 2003) needed on what information consumers actually use, and (Microsoft, 2007). Before validity and reliability testing how consumers use specific information and form food commenced, nutritionists working in the department purchase decisions based on food-labelling information. checked the questionnaire for both content and clarity. Answering these questions will provide useful guidance for Content validity was assessed by experts with a nutrition a tailored food-labelling education campaign that will focus and dietetic background. Both nutrition and dietetic profes- on the key elements pertinent to improving consumers’ label sionals were contacted through an internet listserv group, reading comprehension. the Community Nutrition Group. Using e-mail, a PDF Estimated to be worth d36.6 billion by 2012 (Mintel, version of the draft questionnaire, brief outline of the project 2007), the catering sector has a significant function in and score sheet were distributed to the group. The score everyday life in Britain. Twenty-seven per cent of British sheet listed each question and asked the respondent to score household’s food and drink expenditure is spent on food and the item out of 10 in relation to appropriateness, importance drink (excluding alcohol) outside the home (Defra, 2006). and phrasing. A column was also provided on the score sheet Traditionally, eating out was initiated by a social event or for other/additional comments to be completed as necessary celebratory occasion; however, in today’s fast paced society, by the respondent. Responses were collated and the ques- eating outside the home is often a necessity. As dining out tionnaire was amended as appropriate. increases, it raises the question, should we be seeing the Face validity of the amended questionnaire was assessed by same nutrition and ingredient information when eating out short post-questionnaire interviews with 20 adults represen- as we do when purchasing products in a retail environment? tative of the population being sampled. Care was taken to As calorie information becomes compulsory in New York ensure that the sample interviewed were of varying educa- chain restaurants with 15 or more outlets nationally (New tion level and socio-economic position. Individuals were York City Department of Health and Mental Hygiene, 2007), asked about the questionnaire instructions, layout and it becomes evident that we know very little about the British length. Ease of completion, time to complete and question

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 212 difficulty were also assessed. Respondents were given the completion of the questionnaire. Questionnaire completion opportunity to ask questions and raise queries with ques- time was between 10 and 15 min with the majority of tionnaire items. respondents (80%) completing the questionnaire in Reliability testing was assessed using a convenience sample o10 min. All participants found the questionnaire layout recruited from local business, with the mean time between to be clear and the majority found both the font size and completing the questionnaire at time 1 and at time 2, 7 days questionnaire length ‘just right’. The questionnaire instruc- later. Respondents completing the reliability testing had not tions were considered easy to understand by 80% of been earlier involved with either the content or face validity respondents (with the remaining 20% stating the instruc- testing. Ninety-seven participants were asked to complete tions were ‘neither easy nor difficult to understand’). Despite the questionnaire at time 1 and were informed that they respondents claiming to find elements of the questionnaire would be required to complete a similar questionnaire 1 difficult (in particular Section C of the questionnaire), it week later. Correlation analysis was performed on the should be noted that no sections were omitted. Sixty per cent reliability testing. Each question correlation was required of respondents skipped the frequency question for ‘Other, to be 40.5 and statistically significant for inclusion in the please specify’ in question 1, and as a result, this question final questionnaire. Cronbach’s alpha coefficient was cal- was formatted (shading and font alterations) to maximize culated to assess the internal consistency of similar future responses. Four respondents enquired about the questions. Cronbach’s alpha values beyond 0.70 were meaning of question 4 (‘How frequently do you use nutrition considered satisfactory for inclusion (Bland and Altman, information on food labels?’) and as a result the question was 1997). As a further measure of reliability Item Difficulty amended to include ‘on food labels when buying food’. Index and Item Discrimination Index were calculated for Section C (nutrition label task questions). The Item Diffi- culty Index is determined by calculating the percentage of Readability the population answering the question correctly (P-value). The higher the Flesch Reading Ease Score, the easier the For inclusion, Kline (1993) suggests that the P-value should document is to understand. The questionnaire scored a be between 20 and 80%. The Item Discrimination Index was Flesch Reading Ease Score of 64.7, indicating that the assessed quantitatively by correlating the score for each item questionnaire was of a standard readability level (Flesch, with the total score. Item Discrimination Index correlations 1948). 40.20 are considered suitable for inclusion (Kline, 1986).

Reliability Results Ninety-seven participants, 61 females and 36 males, completed the questionnaire at time 1. Eighty-one participants, Content validity 50 females and 31 males, completed the questionnaire at Twenty-six nutritionists/dietitians responded to the e-mail time 2. The mean time in days between questionnaire request for comments. Of the 26 nutrition professionals, completions was 7 days, with a minimum interval period 84.6% had experience of teaching or advising on food labels. of 6 days and a maximum interval period of 9 days. With the exception of question 2 (‘Where do you read food Internal consistency of frequency of using specific label labels?’), all questions scored highly for importance, appro- attributes (question 1), frequency of dining at specific priateness and phrasing with mean scores above 8.0 for each catering outlets (question 17) and desire to obtain nutri- question. Overall means for importance, appropriateness tional and additional information at catering outlets (ques- and phrasing were 8.77 s.d.±1.41, 8.79 s.d.±1.34 and 8.84 tions 18 and 19) were assessed using Cronbach’s alpha s.d.±1.20, respectively. coefficient. Given that the largest response was obtained at Amendments to the questionnaire included grammatical time 1 (n ¼ 97) and participants had no earlier exposure to changes and the addition of explanatory notes in question 1 the questionnaire at this point, time 1 data was used to assess (with regards to allergen, nutrition and producer informa- Cronbach’s alpha values. Cronbach’s alpha coefficients were tion), emphasis on the terms ‘read’ and ‘use’ in questions 1, 2 0.85, 0.75 and 0.91 for frequency of using specific label and 4, and the addition of ‘workplace canteen’ to questions attributes, frequency of dining at specific catering outlets 15–17. Despite scoring poorly, question 2 (‘Where do you and desire to obtain nutritional and additional information read food labels?’) was not removed as it was felt that this at catering outlets, respectively, showing good internal question provided a valuable insight into label reading consistency. behaviour (pre- and post-purchase). Repeat reliability testing was carried out on the data obtained from the time 2 sample (n ¼ 81). Good temporal stability was shown with Spearman’s correlation coefficients Face validity ranging from 0.51 to 0.97, all significant at Po0.001. Twenty adults from various socio-demographic and educa- Item Difficulty Index analysis was carried out using tional backgrounds completed a short interview after questionnaires completed at time 1 (n ¼ 97). Five out of the

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 213 Table 1 Item difficulty analysis for (the first) Section C

Question Difficulty (% answering correctly)

Locating the calories per 100 g (Question 7) 91.8 Locating the quantity of fat in the package (Question 8) 76.3 Calculating the amount of fibre in half the pack (Question 9) 84.5 Calculating the amount of saturated fat in 200 g of the product (Question10) 79.4 Looking at the sugar content of this product (Question 11) 22.7 Comparing the fat content of two products (Question 12) 82.5 Comparing the saturated fat content of two products (Question 13) 96.9 Comparing the energy content of two products (Question 14) 96.9

eight questions in Section C were answered correctly by Table 2 Spearman’s correlation coefficient for the final version of 480% of the respondents, indicating that they were too easy Section C for inclusion in the final questionnaire (Table 1). On the Question N Test–retest basis of this analysis, this section was revised and indepen- reliabilitya dently underwent reliability testing. Nutrition colleagues working within the research centre C7. Sugar in two servings 51 0.728 were consulted during the revision of Section C. Reliability C8. Grams of fat in half the pack 51 0.779 C9. Servings in the product 51 0.936 testing of the revised Section C was conducted. Participants C10. Fat content in Product 1 51 0.570 received only Section C of the questionnaire and submitted C11. Fat content in Product 2 51 0.772 their post-code for matching purposes; no other demo- C12. Sugar content in Product 3 51 0.891 graphic data was collected. Seventy participants completed C13. Comparison between Products 2 and 3 51 0.790 C14. Lowest saturated fat content 51 0.795 Section C at time 1 and 51 participants completed the C15. Losing weight 51 0.814 questionnaire at time 2 (with the average completion time C16. Reducing salt intake 51 0.616 between questionnaires, 7 days). aSignificant at P 0.001. Internal consistency was assessed using Cronbach’s alpha o on data obtained during time 1 (n ¼ 70). For ability to make judgements on nutrition content from available nutrition information (questions 10–16), the Cronbach’s alpha was altered (from 16–25 to 18–25) to remain consistent with the 0.72, indicating good internal consistency. sample group used. Repeat reliability of Section C was carried out using data Two additional questions were added to the questionnaire. obtained for the 51 participants who completed Section C at Both questions were included in Section E of the question- both time 1 and 2. Spearman’s correlation coefficients naire and assessed the participant’s motivation to eat a ranged from 0.57 to 0.94 and were statistically significant healthy diet (‘How motivated are you to eat a ‘healthy’ diet?) at Po0.001, indicating good temporal stability (Table 2). and their own perceived knowledge of a healthy eating The Item Difficulty Index was re-assessed for the revised (‘How would you rate your own knowledge of ‘healthy Section C. The P-value’s highlighted moderate scores for the eating’ on a scale of 1–10? (1 ¼ no knowledge and 10 ¼ very new questions indicating that they were not as easy as the knowledgeable)’). The final version of the questionnaire initial draft and appropriate for inclusion in the final (excluding Section E—the demographic items) is shown in questionnaire (Table 3). Appendix Table 1. With regards to Item Discrimination Index analysis, all items in Section C achieved correlations above 0.20 (Kline, 1986), with r ranging from 0.43 to 0.70 (Table 3), indicating that these items were suitable for inclusion in the final Discussion questionnaire. The questionnaire development process involved a literature search, reviewing the findings from existing literature and Final adjustments highlighting any gaps in the current research. The review After the reliability and validity assessment, four further highlighted the limited availability of studies reporting the alterations were made to the questionnaire. One amendment development of validated tools used to measure consumers’ was made to question 1 in Section A, the tick box was food label reading habits. To our knowledge, this is the first removed from ‘Other please specify’ (as the majority of study to report the validation and reliability testing of a participants omitted this question, despite earlier font and short questionnaire to assess consumers’ use, understanding formatting alterations). The age range (question 23) was and perception of food labels.

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 214 Table 3 Item analysis for the final version of Section C

Question Difficulty Discrimination (% answering correctly) (item-total r-value)

Sugar content in two servings (Question 7) 51.4 0.57 Grams of fat in half pack (Question 8) 61.4 0.64 Servings in pack (Question 9) 71.4 0.55 Fat content in Product 1 (Question 10) 60.0 0.43 Fat content in Product 2 (Question 11) 38.6 0.53 Sugar content in Product 3 (Question 12) 62.9 0.47 Comparing the saturated fat content of two products (Question 13) 67.1 0.70 Saturated fat content in product with lowest sat fat (Question 14) 28.6 0.50 Losing weight (Question 15) 72.9 0.63 Salt intake (Question 16) 71.4 0.63

In the development of this instrument, special considera- between survey contact; therefore, no changes would be tion was given to developing a questionnaire, which could expected unless enquiry of the subject area was prompted be completed independently, without assistance. It was, by the initial questionnaire exposure. The Spearman’s therefore, important that the readability level of the correlation coefficients (0.51 to 0.97) were statistically questionnaire was pitched appropriately. Care was taken to significant at Po0.001, indicating strong reliability of these avoid long sentences, complex terminology, acronyms or items assessed. abbreviations, double-barrelled and leading questions. Although the optimum value for Cronbach’s alpha varies It is recommended that independently administered throughout the literature (DeVon et al., 2007), a value 40.70 (self-completion) questionnaires are short in length and are is the most commonly accepted figure (Bland and Altman, composed mostly of closed structure questions (McColl et al., 1997). In this study, all values were 40.70 indicating high 2001). Postal questionnaires short in length (Edwards et al., levels of internal consistency in this instrument. 2002) and containing o1000 words (Jepson et al., 2005) are The majority of the participants used in the reliability and more likely to yield a high response rate. Care was taken to validity testing of this questionnaire were both White and ensure that the questionnaire was short in length (only four Scottish. This is recognized as a limitation of this study, as we sides of A4), contained o1000 words and comprised mainly cannot presume that all ethnic groups and nationalities closed end questions (47 out of 49 items). The response would use nutrition labels in the same manner, nor interpret categories in the close structure questions were considered this questionnaire in the same way. Future feasibility testing mutually exclusive and exhaustive after the literature review in different geographic areas or with alternative ethnic of the topic area and the considerable effort used during the groups should be conducted before using this tool as a guide face and content validity process. to inform changes in policy. Various other formatting characteristics were consciously A further limitation of this study is the use of closed applied in the questionnaire construction. Using a booklet questions when assessing consumers’ attitudes to nutrition format with double-sided printing, vertical formats for information in catering establishments. Closed questions are closed structure responses, a font size of 10 points and a not considered suitable when investigating topics we have high text/background contrast were all incorporated into the limited knowledge of (Rattray and Jones, 2007). Although instrument layout, in line with best practice recommenda- accepting the possibility that information yielded from this tions for questionnaire design (McColl et al., 2001). instrument on nutrition information in catering establish- Demographic questions were purposively inserted at the ments may not be representative of the entire population, it end of the questionnaire, as it has been suggested that these is notable that robust content and face validity were questions can be considered threatening (Sudman and performed in the development of this questionnaire, and Bradburn, 1982) or boring (Rattray and Jones, 2007). The future qualitative studies in the topic area will expand on the demographic questions included in this questionnaire were findings derived from this instrument. adapted from existing tools, for example The 2001 Census, The questionnaire developed in this study was intended to The Food Standards Agency Consumer Attitudes Survey and be administered by post, nationwide throughout the UK. The Family and Children’s Study. Further research should involve examining other question- Although the questionnaire underwent vigorous reliability naire administration methods in various settings. For testing, limitations may still remain in the reliability example, administering the questionnaire in a supermarket methodology used. Repeat reliability testing (test–retest) or retail setting may provide valuable information when presumes that exposure to the questionnaire at time 1 does comparing the choices and decisions consumers make not trigger direct investigation of the topic area by the within their own home environment and in a busy retail respondent. In this study, no intervention took place or catering setting.

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 215 Given the short length of the questionnaire, questions Food Standards Agency (2006). Consumer Attitudes to Food included in the final draft were those considered funda- Standards 2005. Food Standards Agency: London. mental to the topic area. Future research in this subject area Food Standards Agency (2007). Consumer Attitudes to Food Standards. Food Standards Agency: London. may result in the expansion of this questionnaire to include Grunert KG, Wills JM (2007). A review of European research more in-depth items, particularly on issues surrounding the on consumer response to nutrition information on food labels. catering industry. J Public Health 15, 385–399. Hawkes C (2004). Nutrition Labels and Health Claims: The Global In conclusion, the final questionnaire is a standardized Regulatory Environment. World Health Organisation: Geneva. (self-complete) instrument for assessing consumers’ use, Higginson CS, Rayner MJ, Draper S, Kirk TR (2002). The understanding and perception of food labels. nutrition label—which information is looked at? Nutr Food Sci 32, 92–99. Institute of Grocery Distribution (1998). Voluntary Nutrition Labelling Guidelines to Benefit the Consumer. IGD. Conflict of interest Jepson C, Asch DA, Hershey JC, Ubel PA (2005). In a mailed physician survey, questionnaire length had a threshold effect on The authors declare no conflict of interest. response rate. J Clin Epidemiol 58, 103–105. Kessler H, Wunderlich SM (1999). Relationship between use of food labels and nutrition knowledge of people with diabetes. Diabetes Educ 25, 549–559. Acknowledgements Kline P (1986). A Handbook of Test Construction. Introduction to Psychometric Design. Methuen & Co Ltd: London. Kline P (1993). The Handbook of Psychological Testing. Routledge: This research was funded by the Food Standards Agency London. Postgraduate Scholarship Scheme. We thank Dawn Mackison, Krukowski RA, Harvey-Berino J, Kolodinsky J, Narsana RT, Desisto TP Tommy Mackison and the staff at the Centre for Public (2006). Consumers may not use or understand calorie labeling in restaurants. J Am Diet Assoc 106, 917–920. Health Nutrition Research for their help with the packaging Levy AS, Fein SB (1998). Consumers’ ability to perform tasks using and dissemination of the questionnaire. nutrition labels. J Nutr Educ 30, 210–217. Mannell A, Brevard P, Nayga RM, Combris P, Lee R, Gloeckner J (2006). French consumers’ use of nutrition labels. Nutr Food Sci 36, 159–168. References Marietta AB, Welshimer KJ, Anderson SL (1999). Knowledge, attitudes, and behaviors of college students regarding the 1990 Black A, Rayner M (1992). Just Read the Label. The Coronary Nutrition Labeling Education Act food labels. J Am Diet Assoc 99, Prevention Group: London. 445–449. Bland MJ, Altman DG (1997). Cronbach’s Alpha. BMJ 314, 572–573. McColl E, Jacoby A, Thomas L, Soutter J, Bamford C, Steen N et al. Council Directive 90/496/EEC of 24 September on nutrition labelling (2001). Design and use of questionnaires: a review of best practice for foodstuffs (1990). Council Directive 90/496/EEC of 24 applicable to surveys of health service staff and patients. Health September on nutrition labelling for foodstuffs. Technol Assess 5, 1–256. Council Directive 2000/13/EC of the European Parliament and of the Microsoft (2007). Frequently asked questions about grammar Council of 20 March 2000 (2000). Council Directive 2000/13/EC proofing in Word. Microsoft Corporation. of the European Parliament and of the Council of 20 March 2000. Mintel (2007). Eating Out Review—Leisure Intelligence. Mintel Interna- 2000/13/EC. tional Group Limited: London. Cowburn G, Stockley L (2005). Consumer understanding and National Institute of Nutrition (1999). Nutrition labeling: use of nutrition labelling: a systematic review. Public Health Nutr perceptions and preferences of Canadians. Ottawa. 8, 21–28. Neuhouser ML, Kristal AR, Patterson RE (1999). Use of food Defra (2006). Family Food in 2004–2005. National Statistics: London. nutrition labels is associated with lower fat intake. J Am Diet Assoc DeVon HA, Block ME, Moyle-Wright P, Ernst DM, Hayden SJ, Lazzara 99, 45–53. DJ et al. (2007). A psychometric toolbox for testing validity and New York City Department of Health and Mental reliability. J Nurs Sch Second Quarter 39, 155–164. Hygiene (2007). New York City Health Code (Repeal and reenact Edwards P, Roberts I, Clarke M, DiGuiseppi C, Pratap S, Wentz R et al. 81.50). (2002). Increasing response rates to postal questionnaires: Rattray J, Jones MC (2007). Essential elements of questionnaire systematic review. BMJ 324, 1183. design and development. J Clin Nurs 16, 234–243. EU (2008). Proposal for a Regulation of the European Parliament and Rothman RL, Housam R, Weiss H, Davis D, Gregory R, Gebretsadik T of the Council on the Provision of Food Information to et al. (2006). Patient understanding of food labels the role of Consumers. Official Journal of the European Union: Brussels literacy and numeracy. Am J Prev Med 31, 391–398. European Heart Network (2003). A systematic review of the research Stuart SA, Schroder M, Hughes A, Bower J (2004). Dimensional on consumer understanding of nutrition labelling. European analysis of schoolchildren’s food label comprehension: a pilot Heart Network: Brussels. study. Int J Cons Stud 28, 135–146. Flesch R (1948). A new readability yardstick. J Appl Psychol 32, Sudman S, Bradburn N (1982). Asking Questions. A Practical Guide to 221–233. Questionnaire Design. Jossey-Bass Inc.: California.

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 216 Appendix Table 1 Food label questionnaire Please complete sections A, B, C, D ane E

European Journal of Clinical Nutrition Short questionnaire assessing food label use and understanding D Mackison et al 217

European Journal of Clinical Nutrition