Quantitative measures were used to gather data in Phase II of data collection which comprised studies 2 and 3 (see Figure 2.1). Quantitative research is underpinned by an objective, deductive approach that uses mathematical and statistical techniques to measure/count/calculate relationships between variables in a logical, reductionist way in order to test an a priori theory (Yilmaz, 2013). Issues highlighted in Phase I of data collection helped identify issues that required further investigation. Quantitative
methods were deemed the most appropriate way of addressing those issues and research was undertaken to identify appropriate instruments that would produce valid (i.e. it measures what it is designed to measure) and reliable (i.e. it consistently measures the same thing) data (Bryman, 2012; Heale & Twycross, 2015). However, a criticism levied at quantitative research methods include inability to reflect real life/social situations in
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relation to the context in which data were collected. Furthermore, the reliance on instruments to collect data does not reflect real life experiences and the analysis of the relationship between variables and produces a static view of life that is artificial and does not reflect social reality. However, the pragmatic, mixed methods approach
adopted for this thesis and the earlier qualitative phase of data collection helped provide information about context, enabling interpretation of the real-life situation in which quantitative data were collected.
In Study 2, data on child holiday club attendees’ nutritional intake were recorded in retrospective extended 24-hour food recall diaries which were completed by the child’s parent/carer in conjunction with the researcher. In Study 3, data on children’s
performance in word spelling, word reading and maths computation were obtained using the appropriate sub-tests of the Wide Ranging Achievement Test (4) (WRAT 4)
produced by Pearson Education. The following sections outline these quantitative methods and measures in further detail, including the sampling framework and validity and reliability of these measures.
2.5.1. Study 2: Quantitative Data Collection
A range of methods can be used for collecting dietary intake data. Options include a retrospective food recall diary, whereby dietary intake over a specific period of time (usually 24 hours) is recalled producing a pattern of usual consumption of food types and amounts consumed. Though time consuming to complete, retrospective food recall diaries place less of a burden on respondents compared to prospective dietary records, but are researcher resource intensive (Bates, Bogin, & Holmes, 2011). They require participants to have a good understanding of and ability to gauge portion size which are usually estimated using household measures (e.g. bowls, cups, spoons) (Bates et al., 2011). An alternative approach is to use photographs of food portion sizes, for example within the UK “A photographic atlas of food portion sizes” (Nelson, Atkinson, & Meyer, 1997) which depicts images of 76 of the most widely consumed foods in the British diet. It is considered that the use of photographs improves the accuracy of portion size data compared to using household measures to estimate portion sizes.
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However, the use of adult size portions of food leads to over-reporting of intake by children (Foster et al., 2006). To address this limitation in collecting portion size data on children’s dietary intake, a series of children’s food atlases have been developed which depict various portion sizes of the 100 most common items of food and drink consumed by children in the UK (Foster, Hawkins, & Adamson, 2012). Whilst accuracy in terms of gauging portion sizes of food consumed by children can be improved by using photographs of child appropriate portion sizes of food, a limitation of the retrospective 24-hour recall diary is that intake over one 24-hour period reflects may not produce a realistic picture of habitual intake as, for example, dietary intake patterns often differ at weekends when more unhealthy food is consumed compared to dietary patterns during the week when healthier food is eaten (An, 2016). An alternative to the retrospective 24- hour food diary is the completion of a prospective food diary which is typically
completed over a minimum of four days. This method is used to collect nutritional intake data in the National Diet and Nutrition Survey, which is a rolling programme which collects dietary intake in a representative sample of the UK population.
Participant’s record every item of food and drink consumed in the time period and either weigh food portions prior to consumption and weigh any leftover food or alternatively use household measures to gauge portion sizes. Completion of a prospective food diary therefore requires good literacy skills amongst participants so use may be more limited in populations with low literacy skills (Bates et al., 2011). Furthermore, this method of data collection places a heavy burden on respondents, who may alter their eating behaviour to accommodate completion of a weighed food diary (Foster et al., 2006). Food frequency questionnaires offer an easier, quicker alternative to food diary
completion. Participants are provided with a pre-printed list of foods which may contain information on portion sizes and space may be provided to include foods consumed but not included in the pre-printed list (Bates et al., 2011). Although less burdensome than food diaries for participants, food frequency questionnaires are limited in that they are less precise in the amount of data provided (Bates et al., 2011).
Regardless of the method chosen to record dietary intake, most dietary intake methods are prone to error including mis-reporting and particularly under-reporting of intake
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(Hill & Davies, 2001; Maurer et al., 2006). Furthermore, collating data on children’s nutritional intake poses a number of additional challenges (Foster & Adamson, 2014). Completing a dietary recall measure requires not only a good memory, but also the ability to understand the information being requested, the ability to search for and evaluate the information being requested and responding to the request (Livingstone, Robson, & Wallace, 2004). Parents and carers act as the nutritional gatekeeper of children and therefore control access to food and drinks so will usually complete dietary intake records for children younger than 7-8 years of age, although when children are out of the home environment and cared for by others, this may weaken the accuracy of data collected (Foster & Adamson, 2014). However, by the age of 7-8 years, it is considered that children have the cognitive skills to be able to undertake this task, though the time frame to ensure more accurate recall is limited to the previous 24 hour period and completion is best suited to a time when regular meal patterns are observed, rather than at weekends or holidays when eating patterns may be more irregular
(Livingstone et al., 2004). By the age of 12 years, children are considered to be able to more accurately gauge portion sizes though their food vocabulary and food knowledge may be limited which may therefore limit the accuracy of intake reports (Livingstone et al., 2004). Furthermore, under-reporting of intake of less healthy items of food observed in adults when completing dietary intake records has also been observed in children aged 9-11 from low SES backgrounds and amongst children with behavioural issues (Moore, Tapper, Moore, & Murphy, 2008).
Having considered all of the relevant factors with regard to collecting dietary intake data, for Study 2, parents/carers were requested to provide dietary intake for their child/children’s intake in a retrospective food diary which was completed in association with the researcher. This approach was taken in order limit potential weaknesses in collecting data from children. In addition, although a 24-hour period of time is a more common time frame for collecting data on nutritional intake, an extended period of data collection was used in Study 2 to enable data to be collected on children’s nutritional intake from lunch time on the day before children attended holiday club, up to and including lunch served at holiday club to enable a comparison of intake during the lunch
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time meal on a day children did not attend holiday club with intake on a day children attended holiday club as well as analysis of fruit and vegetable and water consumption on a typical day during the summer holidays. To enhance accuracy of data collection, the children and young person’s food atlas developed by Foster et al., (2012) was used to gauge food portion sizes served to and consumed by children at each eating and drinking occasion throughout the period of time covered by the diary.
2.5.2. Study 2: Data Analysis
For study 2, data on food intake was recorded in the retrospective extended 24-hour food diaries and the Young Person’s Food Atlas (Foster et al., 2012) was used to capture data on portion sizes. Data on the portion size of every item of food and drink consumed on every eating and drinking occasion over the period covered by the diary by every child was entered into Microdiet nutritional analysis software to obtain data on the energy and macronutrient content of each item of food and drink. Every item of food and drink consumed by each child for lunch each day was coded as either a core or non- core item of food. Classification of a food item as either core or non-core is based upon Australian dietary guidelines (Grimes, Riddell, & Nowson, 2014). More information on classification of food as core and non-core items is provided in Chapter 4 (see page142). This data was then entered into a database created in SPSS v.24 and were subject to analysis by means of a Repeated Measures ANOVA.
2.5.3. Study 2: Validity and Reliability
In quantitative research, validity refers to the extent to which a concept is accurately measured and reliability refers to the accuracy of the instrument used and if it consistently produces the same results across a similar sample (Heale & Twycross, 2015). With regard to collecting data on dietary intake, validity refers to the ability of the tool used to capture data that represents the true intake of the participant (Burrows et al., 2013). The gold standard against which all other dietary intake measures are
assessed is the use of doubly labelled water method in which participants ingest a sample of water where the hydrogen has been labelled with deuterinium and the oxygen has been labelled with oxygen-18 and the rate at which it is eliminated from the body (in
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saliva or urine samples) is measured over a period of 7-14 days to give an accurate measure of total energy expenditure. Although easy to administer and accurate, this method is expensive to use. In a systematic review of the validity of dietary assessment measures in children compared to using doubly labelled water, the use of 24-hour multiple pass recall diary over a period of three days, including weekdays and weekends, was found to be the most accurate measure to estimate energy intake of children aged 4-11 years compared to use of doubly labelled water (Burrows, Martin, & Collins, 2010). However, completion of three day 24 hour recall diaries places a high burden on respondents. It was considered that it was not feasible, viable, or relevant to collect this much data from the sample population in Study 2.