A sample of approximately 300,000 young people were selected from the National Pupil Database (NPD) and contacted to take part in the postal survey, with the option to complete it online. Fieldwork ran between 22nd September 2014 and 9th January 2015. A total of 120,115 participants responded to the survey. A £5 shopping voucher was used as the token of appreciation, which was conditional on completing the questionnaire. The response rate was 41%, when taking into account any undeliverable mail outs and opt-outs from the sampled pupils.
With diet-related questions in the WAY postal survey, findings are dependent on the 15 year old being able to determine a portion size with no help. To assist in this, the diet related questions in the WAY survey all included examples of the type of fruits, vegetables, pulses and drinks in question, as an example of a portion size (such as 3 heaped tablespoons or medium sized glass).
By using the NPD as a sampling frame, it was possible to stratify the sample to help ensure the sample was representative across a range of pupil and area characteristics. Data were weighted by gender, ethnicity, Free School Meal eligibility, quintile of the Index of Multiple Deprivation, and local authority to reflect the known population profile of 15 year olds in England (sourced from the NPD).
Both the numerator and the denominator are weighted to make them applicable to the population as a whole. Further details on the sampling methodology and weighting procedure can be found in the WAY survey technical report
The confidence intervals for each ethnic group are available in Download the data.
Based on survey responses, it’s estimated that 51.1% of White 15 year olds surveyed ate 5 portions of fruit or vegetables in the day prior to the survey. Because the WAY survey questioned a sample of 15 year olds rather than all 15 year olds, however, it’s impossible to be 100% certain of the exact percentage.
It’s 95% certain, however, that between 50.8% and 51.3% of all White children ate 5 portions of fruit or vegetables in the day prior to the survey. In statistical terms, this is a 95% confidence interval, with a lower and upper confidence interval of 50.8% and 51.3% respectively. This means that if 100 random samples were taken, then 95 times out of 100 the estimate would fall between the lower and upper confidence interval. But 5 times out of 100 it would fall outside this range.
The smaller the survey sample, the more uncertain the estimate and the wider the confidence interval. For example, fewer 15 year olds from the Other ethnic group were sampled for this survey than White 15 year olds, so we can be less certain about the estimate for the smaller group. This greater uncertainty is expressed by the wider confidence interval of between 62.4% and 67.4% for 15 year olds from the Other ethnic group.
Statistically significant findings have been determined where the 95% confidence intervals of an ethnic group do not overlap with the value for all ethnicities combined (52.4%).
Percentages are rounded to 1 decimal place.Quality and methodology information