National Child Measurement Programme annual report

Data quality statement

Purpose of document

This data quality statement aims to provide users with an evidence-based assessment of quality of the statistical output included in this report.

It reports against the 9 European Statistical System (ESS) quality dimensions and principles appropriate to this output. In doing so, this meets the Department of Health and Social Care’s (DHSC’s) obligation to comply with the UK Statistics Authority Code of Practice for Statistics, and the following principles in particular:

  • trustworthiness pillar, principle 6 (Data governance) which states “Organisations should look after people’s information securely and manage data in ways that are consistent with relevant legislation and serve the public good.”
  • quality pillar, principle 3 (Assured Quality) which states “Producers of statistics and data should explain clearly how they assure themselves that statistics and data are accurate, reliable, coherent and timely.”
  • value pillar, principle 1 (Relevance to Users) which states “Users of statistics and data should be at the centre of statistical production; their needs should be understood, their views sought and acted upon, and their use of statistics supported.”
  • value pillar, principle 2 (Accessibility) which states “Statistics and data should be equally available to all, not given to some people before others. They should be published at a sufficient level of detail and remain publicly available.”

Note: The original quality dimensions are relevance, accuracy and reliability, timeliness and punctuality, accessibility and clarity, and coherence and comparability; these are set out in Eurostat Statistical Law. However more recent quality guidance from Eurostat includes some additional quality principles on output quality trade-offs, user needs and perceptions, performance cost and respondent burden, and confidentiality, transparency and security.


Impact of the Covid-19 pandemic on the NCMP

The 2018 to 2019 school year was the last complete collection of NCMP data before the pandemic that was unaffected by COVID-19.

The 2019 to 2020 NCMP collection was incomplete as no measurements were taken after March 2020, when schools were closed as part of the COVID-19 pandemic response. Data quality work was undertaken on the 2019 to 2020 data which established that this collection year is comparable to earlier years at the England level. It can be used to look at England level statistics just before the pandemic started. The impact at local authority level was more variable. Please refer to the 2019 to 2020 Data Quality section of the NHS England report for further information. Within the report, comparability for regions and the deprivation analyses are also described.

The COVID-19 pandemic had the greatest impact on the 2020 to 2021 school year collection. The NCMP did not officially open at the start of the academic year. Instead in March 2021, local authorities were asked to collect a representative sample of child measurements to enable a national estimate of child obesity for 2020 to 2021 and contribute towards assessing the impact of the pandemic on children’s physical health. Full details of the approach, methods and results are available in the Methodology and Data Quality section of the 2020 to 2021 NHS England NCMP report.

The 2021 to 2022 data was the first complete NCMP year since the pandemic, with the collection starting on 01 September 2021. During the academic year, there continued to be some disruption due to COVID-19 outbreaks. Data quality work undertaken on the 2021 to 2022 NCMP dataset identified that a higher-than-normal proportion of local authorities conducted their measurements between March and July 2022. It is also anticipated that absences due to the pandemic may have reduced the participation rate in certain local authorities where children were absent from school on the days the measurements were taken.

In the following years, the participation rate increased. Participation rates for the latest and previous collection years for each local authority, region and England are published in the obesity, physical activity and nutrition profile on Fingertips.


Relevance

This dimension covers the degree to which the statistical product meets user needs in both coverage and content.

The NCMP covers children aged 4 to 5 years and 10 to 11 years attending mainstream state-maintained schools in England.

For each collection year, local authorities are assigned a list of mainstream state-maintained schools within their area, along with associated reception and year 6 headcounts (based on Department for Education school census data).

The proportion of returned schools and measured children are assessed at the end of the collection to check that coverage falls within acceptable thresholds. Further information on data quality of key fields in the NCMP dataset is provided at national level in the methods report and at local authority level in table 12 of the data tables that accompany the report.

Coverage against each data item is also assessed and more details are provided in the following section.

Information in the analysis report is presented by the following breakdowns:

  • age
  • sex (at birth)
  • deprivation
  • ethnicity
  • geography


Accuracy and reliability

This dimension covers, with respect to the statistics, their proximity between an estimate and the unknown true value.

The accuracy and reliability of the dataset underpinning the analyses in the report is ensured by a rigorous validation procedure. Further details are provided in Validation of National Child Measurement Programme data.

As records are submitted, the NCMP system checks that all mandatory data items have been provided and data validation rules have been met:

  • records with missing data items are rejected
  • invalid data items (such as incorrect ethnicity codes) are rejected
  • unexpected data items (such as ‘extreme’ heights) generate warning flags that requires the submitting local authority to confirm that the data are correct

The NCMP system provides local authorities with real-time data quality indicators throughout the collection period. Indicators breaching the data quality thresholds are highlighted. This enables local authorities to monitor the quality of their data during the collection period and take action if necessary. The data quality thresholds are provided in the validation document mentioned above. The local authority’s NCMP Lead is required to sign off these indicators as part of finalising their data at the end of the collection. Indicators breaching the thresholds require the NCMP Lead to provide a breach reason before it is possible to finalise the submission.

The performance of local authorities against these data quality measures, along with breach reasons where applicable, is provided in the accompanying data tables spreadsheet in table 12.

In recognition of the effect of natural year to year variation, confidence intervals are included around the prevalence estimates and these should be considered when interpreting results. A confidence interval gives an indication of the sampling error around the calculated estimate and takes into consideration the sample sizes and the degree of variation in the data. They are used to determine whether any differences in prevalence figures are likely to be real or due to natural variation.

The sample sizes and participation rates for NCMP are usually large. Over one million children have been measured, with a participation rate exceeding 90%, for every collection year since 2008 to 2009 (with the exception of the 2019 to 2020 and 2020 to 2021 collection years which were impacted by COVID-19). The 95%confidence intervals for prevalence estimates at national level are very narrow which indicates a small margin of potential error.

Comparisons between groups and over time have been statistically tested, at a 95% significance level, to determine whether differences are likely to be genuine (statistically significant) or the result of random natural variation. Only statistically significant differences have been described with terms such as “higher”, “lower”, “increase” or “decrease”. When a comparison does not show a statistically significant difference, this will be described using terms such as “similar to” or “the same as”. The comparisons that feature in the report have all been tested. Further details are provided in the Methods report of the publication.


Timeliness and punctuality

Timeliness refers to the time gap between publication and the reference period. Punctuality refers to the gap between planned and actual publication dates. The NCMP national report is published annually and has never missed a scheduled publication date. The annual report is released each year just under 3 months from the end of the submission period.


Coherence and comparability

Coherence is the degree to which data which have been derived from different sources or methods but refer to the same topic are similar. Comparability is the degree to which data can be compared over time and domain.

The Health Survey for England (HSE) contains prevalence for different BMI categories. The HSE covers all children and is not restricted to those in reception or year 6. It is based on a much smaller sample therefore the confidence intervals around the estimates are much wider than those presented in this report. These confidence intervals have been getting wider in recent years as fewer children have taken part in the HSE.

A comparison between the data in the 2007 to 2008 NCMP and the HSE 2007, and between the 2008 to 2009 NCMP and the HSE 2008, was published in Chapter 13 of the HSE 2008.

Overweight and obesity prevalence estimates for single year of age for children (age 2 to 15 years) were published by NHS England using HSE 2015 to 2019 and 2022 combined.

The report contains links to data published relating to children in Wales, Scotland and Northern Ireland.


Accessibility and clarity

Accessibility is the ease with which users can access the data, also reflecting the format in which the data are available and the availability of supporting information. Clarity refers to the quality and sufficiency of the metadata, illustrations and accompanying advice.

The NCMP data can be viewed in various formats including an accessible spreadsheet, html report and in the obesity, physical activity and nutrition profile on Fingertips.


Trade-offs between output quality components

This dimension describes the extent to which different aspects of quality are balanced against each other.

A small number of children move schools during the school year and therefore could be measured more than once depending on when the measurements take place in the schools they have attended. This is a necessary trade-off since local authorities have a statutory responsibility to measure children in mainstream state-maintained schools regardless of whether these children have been measured previously or not.


Assessment of user needs and perceptions

This dimension covers the processes for finding out about users and uses and their views on the statistical products. This report, previously published by NHS England, was part of a cross-publication consultation launched in December 2023. The outcome of the consultation was that DHSC and NHS England NCMP outputs will merge, with DHSC taking responsibility for the publication of the annual reporting of data from the NCMP from autumn 2025.

Previously this report was part of a consultation on all NHS Digital publications in 2016. In response to user feedback gathered from this consultation the report was reformatted with extensive written content being replaced by headline results and associated graphics. These presentation techniques were in line with other reports already being produced by NHS England which had received positive feedback from users.

The 2015 to 2016 report underwent a review managed by the Government Statistical Service (GSS) Good Practice Team where a team of 7 GSS colleagues reviewed the report and made suggestions for improvements. Most of these suggested improvements were implemented.

Ad hoc requests for NCMP data inform the content of published tables during the design and development stage of the publication each year. The DHSC is keen to gain a better understanding of the users of this publication and of their needs; feedback is welcome and may be sent to .


Performance, cost and respondent burden

This dimension describes the effectiveness, efficiency and economy of the statistical output.

The legal foundation for the NCMP is provided in local authority regulations, the statutory duty provides the legal basis under UK General Data Protection Regulation (UK GDPR). This means that all local authorities must take steps to ensure parents are informed that their child will be measured and the information will be processed as part of the NCMP. Parents must be given an opportunity to withdraw their child from participating in the programme. Local authorities contact parents of all children eligible to participate in the NCMP via email or parent-school portals to share a pre-measurement letter and NCMP privacy notice. Parental consent is not the lawful basis for the processing of NCMP data. Children not withdrawn by their parents or themselves are then measured and their data and other details are entered into the NCMP data collection system.

The measurement of children’s heights and weights, without shoes and coats and in normal, light, indoor clothing, is overseen by health and care professionals and undertaken in school by trained staff. DSHC provides guidance to local authorities on how to accurately measure height and weight.

Data are provided annually by local authorities and published by DHSC. Some local authorities choose to share a child’s measurements to parents by either generating a letter, using the NCMP data collection system or contacting them via other parent communication platforms and are encouraged to do so within six weeks of the measurements being taken.

The cost for NHS England to collect, validate and provide support to local authorities and service providers was around £200,000 in 2024 to 2025. This includes hosting, maintaining and enhancing the NCMP IT collection system. All local authorities in England receive finances via their annual Public Health Grant to collect and submit the measurement data of all children eligible to be measured as part of the NCMP. Annual expenditure data is available for individual local authorities in their social care and public health services outturn, local authority revenue expenditure and financing.


Confidentiality, transparency and security

The procedures and policy used to ensure sound confidentiality, security and transparent practices.

New disclosure control processes were applied to all outputs in NCMP for 2019 to 2020 and going forwards. Full details of the new methodology are available in the methodology change notice.

The data contained in this publication are Accredited Official Statistics. The code of practice for official statistics is adhered to from collecting the data to publishing.