Digital Skills In Northern Ireland – Supplementary Document
Digital Skills In Northern Ireland – Supplementary Document
The Digital Skills in Northern Ireland report examines the digital skill level of people in Northern Ireland, sourced from the Continuous Household Survey (CHS).
The Further Information section (section 4) of the report contains an overview of key topics, and this document aims to provide additional background information, including further detail on the CHS (primarily sourced from the CHS survey documents) and the methodology.
1. The Continuous Household Survey (CHS)
1.1 Background
The Continuous Household Survey (CHS) is the longest-running
continuous social survey carried out in Northern Ireland, conducted by
the Central Survey Unit (CSU) of the Northern Ireland Statistics and
Research Agency (NISRA). The dataset used for this publication is from
April 2023 to March 2024.
The CHS is designed to provide an
ongoing snapshot of social and economic conditions in Northern Ireland.
It is carried out continuously to ensure that the information is always
up to date and reflects everyday life and conditions in Northern Ireland
today. The survey asks questions on a variety of topics, such as
internet access, the environment, tourism, libraries, health, sport and
education.
1.2 The questionnaire
The questionnaire has two distinct parts; a household schedule and an
individual schedule. One person on behalf of the entire household
answers the household schedule, while all participating adults in the
household answer the individual schedule.
In a change to previous 2 years, the questionnaire returned to a
split sample. This means that depending on the serial number of the
questionnaire (even or odd) the respondents would be exposed to a
different set of questions for part of the questionnaire. This was
implemented to reduce survey length.
1.3 The fieldwork and sample size
Fieldwork starts on 1 April 2023 and ends on the 31 March 2024.
Addresses are split across the 12 months, with approximately a 10%
reduction in allocations in July, August and December to allow for
reduced interviewer availability in these months.
In 2023/24, 4,113 households took part in the survey. When
ineligible addresses are discounted from the sampling frame this gives a
survey response rate of 50%. Within those 4,113 households, a total of
4,927 individuals took part in the survey (1.2 individuals per
household).
Table 1: Sample sizes from the Continuous Household Survey 2023/24 (by age and gender), aged 16 and over, April 2023 to March 2024
| Characteristic | n |
|---|---|
| Age | |
| 16 to 24 | 192 |
| 25 to 34 | 562 |
| 35 to 49 | 1,191 |
| 50 to 64 | 1,402 |
| 65 and over | 1,580 |
| Gender | |
| Males | 2,157 |
| Females | 2,770 |
| Base = 100% | 4,927 |
2. Methodology and Quality Information
2.1 Representativeness of the sample
In any survey there is a possibility of non-response bias.
Non-response bias arises if the characteristics of non-respondents
differ from those of respondents in such a way that they are reflected
in the responses given in the survey.
Accurate estimates of non-response bias can be obtained by
comparing characteristics of the achieved sample with the distribution
of the same characteristics in the population at the time of sampling.
Such comparisons are usually made to the current Census of Population
data.
To assess how accurately the Continuous Household Survey sample
reflects the population of Northern Ireland the sample has been compared
with characteristics of the Northern Ireland population from Mid-Year
Population Estimates.
Table 2: Mid-Year population estimates and the Continuous Household Survey respondents
| Characteristic | Mid-Year Population estimates 2020 (%) | CHS 2023/24 (%) |
|---|---|---|
| Age | ||
| 16 to 24 | 13% | 4% |
| 25 to 34 | 16% | 11% |
| 35 to 44 | 17% | 16% |
| 45 to 54 | 17% | 18% |
| 55 to 64 | 16% | 19% |
| 65 and over | 22% | 32% |
| Gender | ||
| Male | 49% | 44% |
| Female | 51% | 56% |
| Base = 100% | 1,521,108 | 4,927 |
2.2 Weighting
In order to estimate the number of people at each digital skill level, it is necessary to gross the findings from the survey to the NI population. The respondent data is weighted to the NI population by local government district, age group and sex. This ensures that the sample is representative of the overall NI population.
The sample is split into seven age groupings for both sexes in each local government district resulting in 182 weighting cells. The age groups used for weighting were 16 to 24, 25 to 34, 35 to 44, 45 to 54, 55 to 64, 65 to 74, and 75 and over.
2.3 Sampling Error
No sample is likely to reflect precisely the characteristics of the population it is drawn from because of both sampling and non-sampling errors. An estimate of the amount of error due to the sampling process can be calculated. For a simple random sample design, in which every member of the sampled population has an equal and independent chance of inclusion in the sample, the sampling error of any percentage, p, can be calculated by the formula:
\[ s.e. (p) = √(p*(100 – p)/n \] where n is the number of respondents on which the percentage is based.
The sample for the Continuous Household Survey is drawn as a random sample, and thus this formula can be used to calculate the sampling error of any percentage estimate from the survey. A confidence interval for the population percentage can be calculated by the formula:
95% confidence interval \[
p+/- 1.96 * s.e. (p)
\] If 100 similar, independent samples were chosen from the same
population, 95 of them would be expected to yield an estimate for the
percentage, p, within this confidence interval. The absence of design
effects in the survey, and therefore of the need to calculate complex
standard errors, means that standard statistical tests of significance
(which assume random sampling) can be applied directly to the
data.
Table 3 shows the sampling variability of digital skill level of NI
respondents using 95% confidence intervals. We would expect that in 95%
of samples the range would contain the true value.
Table 3: Sampling variability of digital skill level in Northern Ireland, aged 16 and over, April 2023 to March 2024
| Digital skill level | Proportion of aged 16 and over (%) | Lower limit (%) | Upper limit (%) |
|---|---|---|---|
| No skills | 22.8 | 21.6 | 24.0 |
| Novice skills | 28.8 | 27.6 | 30.1 |
| Intermediate skills | 23.3 | 22.1 | 24.5 |
| Advanced skills | 25.1 | 23.9 | 26.3 |
3. Contact
If you require further information or would like to provide feedback please contact:
Patrick O’Kane
Email: Patrick.OKane@nisra.gov.uk
Web: Digital
skills in Northern Ireland