The proximity between an estimated value and the true value.
The accuracy of the data is the responsibility of the Local Authorities who submit the data to NHS Digital. The SSDA902 return is an aggregate collection and as NHS Digital does not have access to the individual records behind the aggregate counts, we are reliant on Local Authorities to assess their own data quality.
The submission and validation process for each collection is carried out as follows:
- The Local Authority collates the data for submission in the relevant collection form. This form includes inbuilt validations to allow councils to check their data for common issues prior to submission.
- Local Authority submits data by the mandated deadline
- All Local Authorities who met the deadline receive a data quality report covering critical validations and also providing some derived totals allowing councils to confirm their data is correct
- NHS Digital reviews the quality of all files submitted and may provide additional support to local authorities with significant data quality issues
- Local Authorities are able to resubmit data to amend any identified quality issues
- Final deadline for submission
- Following the final deadline NHS Digital will carry out analysis of the quality of final deadline. Although Local Authorities cannot resubmit data after this point, they may be contacted for additional clarification or context.
The validation checks carried out throughout this process include:
- Checks for missing data items
- Checks against the previous collection
The final validations consisted of looking at the responses to validation checks mentioned above to see if there are clear instances where data are implausible or Local Authorities have submitted data not in line with the guidance for the data collection and contacting the councils where necessary.
Common issues councils advised us of include: disability data not being routinely recorded, difficulties accessing data on clients aged under 18 and deceased clients not being removed from the register.
People that have a Certificate of Vision Impairment from an ophthalmologist choose whether or not to be included in their Local Authority’s register of blind or partially sighted people; registration is not automatic. This means that not everybody that has been certified as having vision impairment is recorded on a Local Authority register. For this reason, the data in this publication cannot be considered as definitive numbers of blind and partially sighted people.
The statistics relating to blind people who have an additional disability may understate the true numbers. This is partly because there is no advantage to a blind person in being registered as having additional disabilities.
Where there was information on additional disabilities for people having multiple disabilities including deaf or hard of hearing, Local Authorities were advised to count this under the category of deaf or hard of hearing. This could lead to a bias towards deaf or hard of hearing disabilities.