As the Dental Working Patterns Survey results are based on a sample, the findings are weighted, to present the results for the overall population. To achieve this, the population is stratified, and appropriate weights are applied to minimise the effect of any bias in the constitution of the sample.
All dentists included in the analysis answered every (relevant) question on the survey.
Dentists were invited to participate in the survey using data provided as follows:
- Data from NHS Business Services Authority (NHS BSA) were used to derive the population of dentists in England and Wales. Dentists were allocated to strata according to:
- dental type (in England only)
- gender
- age
- The Northern Ireland Health and Social Care Business Services Organisation (BSO) and NHS National Service Scotland, Information Services Division (ISD) provided data relating to the primary care dentist populations for Northern Ireland and Scotland respectively. Because of the smaller populations in these countries, dentists were allocated to the same strata as used for Wales:
2018/19 survey results were weighted to the final dental populations effective on 31 March 2019. However, final-year data were not available for all countries at the time the report was produced and as a result, the mid-year dental workforce populations on 30 September 2019 were used to weight the 2019/20 results. The effect of using the mid-year data has been tested and found to be minimal and enables us to release the report in time for consideration by the DDRB which better meets the needs of users and other stakeholders.
For each country grouping – England, Northern Ireland, Scotland, and Wales – one set of weighting factors are derived based on the strata, and the same set of weights are applied throughout. Further information is available in the Methodology .
As the results are weighted to the full-year self-employed dental population they are subject to sampling error and uncertainty. This is because using information from or about a sample of the population can never be as accurate as using information for the entire population. Apparent differences between groups and sub-group of dentists, or in results compared to the previous years may therefore not be statistically significant. In addition, small dental populations for some sub-groups mean that extreme values can have noticeable effects on the averages; in such cases, results may be subject to more uncertainty.
Statistical significance is used in this report to illustrate the extent to which users can be confident that differences between compared results are not due to chance.
Dental population figures cited in the report should not be regarded as the definitive dental populations, and they will not be the same as those published in NHS Dental Statistics for England or comparable country reports produced by NHS Digital. This is because some dentists are excluded from the DWP Survey results for methodological or data quality reasons (for example, the results are based only on those dentists that worked for a full year discounting any annual leave taken). More detail on the dental populations is in the Methodology.
All changes to the methodology, structure, content and presentation of results are discussed by the DWG prior to implementation. In addition, at each stage the report is further validated and quality assured by NHS Digital analysts unconnected with its production.