1. Methodology background


 National Statistic   
 Survey name  Opinions and Lifestyle Survey (OPN)
 Frequency  Monthly
 How compiled  Sample based survey
 Geographic coverage  Great Britain
 Sample size  1,200
 Last revised  11 September 2012

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2. Overview

  • data are collected using face-to-face interviews over a 4 week period
  • a sample of 2,010 households is drawn from the Postcode Address File (PAF) every month, and from this, approximately 1,200 face-to-face interviews are conducted with adults (aged 16 or over)
  • the survey has a maximum turnaround of 14 weeks

The Opinions and Lifestyle Survey (OPN) is a monthly face-to-face omnibus survey designed to be a fast, cost effective and reliable way of collecting information on a variety of topics that are too small to have surveys of their own.

The survey provides this service for a number of clients, such as government departments, charities and academics. Various topics are run for a variety of clients every month, producing a diverse questionnaire that collects timely data for research, policy analysis and campaign evaluation.

The survey has a number of modules covering a range of subject areas each month. This allows organisations to gather data on topics of immediate interest. With a maximum turnaround of 14 weeks, clients receive results quickly.

Once fieldwork, data cleaning and processing are complete, clients are sent a dataset for their questionnaire topic, including classificatory variables, such as demographic and household information.

Topics that have been previously commissioned on the survey include smoking habits, cancer awareness, charitable giving, climate change and disability.

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3. Executive summary

The Opinions and Lifestyle Survey is a monthly omnibus survey designed to be a fast, cost-effective and reliable way of obtaining information on a variety of topics too brief to warrant surveys of their own. The survey offers this service for government departments, charities and academics. Various topics are run for a variety of clients every month, producing a diverse questionnaire, which collects timely data for research, policy analysis and campaign evaluation.

A sample of 2,010 households is drawn from the Postcode Address File (PAF) every month. From this, approximately 1,200 face-to-face interviews are conducted with adults (aged 16 or over) in private households in Great Britain each month.

Once fieldwork, data cleaning and processing are complete, clients are sent a dataset for their questionnaire module (topic) including classificatory variables such as demographic and household information. Clients are also sent sampling errors for module and classificatory variables as well as frequencies and a technical report.

This report contains the following sections:

  • Output quality
  • About the output
  • How the output is created
  • Validation and quality assurance
  • Concepts and definitions
  • Other information, relating to quality trade-offs and user needs, and
  • Sources for further information or advice
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4. Output quality

This report provides a range of information that describes the quality of the output and details any points that should be noted when using the output.

We have developed Guidelines for Measuring Statistical Quality; these are based upon the five European Statistical System (ESS) Quality Dimensions. This report addresses the quality dimensions and important quality characteristics, which are:

  • relevance
  • timeliness and punctuality
  • comparability and coherence
  • accuracy
  • output quality trade-offs
  • assessment of user needs and perceptions
  • accessibility and clarity

More information is provided about these quality dimensions in the following sections

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5. About the output

Relevance

(The degree to which the statistical outputs meet users’ needs.)

As the survey is a monthly, multipurpose survey collecting information on a variety of topics for the clients that commission the questionnaire modules, data are always relevant for the users.

The Opinions and Lifestyle Survey is used for:

  • providing quick answers to questions of immediate policy interest
  • measuring the efficacy of publicity campaigns
  • measuring public awareness of new policies
  • providing a sample of respondents for follow-up investigations (subject to respondents’ consent; personal information is never linked to survey responses)
  • question testing and piloting
  • testing questions on subjective well-being, including split-sample trials

Topics that have been commissioned on the survey include smoking habits, cancer awareness, charitable giving, climate change and disability.

Strengths and limitations

One of the main strengths of the Opinions and Lifestyle Survey is that it allows customers to receive results quickly; the survey has a maximum turnaround of 14 weeks. Modules can be booked on the survey several months in advance, but the survey is flexible and responsive allowing clients to be included with little notice when necessary.

The survey design allows it to carry a number of modules covering a range of subject areas. The survey is run monthly and allows organisations to gather data on topics of immediate interest. Furthermore, the training of the interviewers and the nature of the Opinions and Lifestyle Survey allows the questionnaire to include sensitive questions. Thus, questions can be piloted prior to their inclusion on larger mainstream surveys.

The monthly sample size of the Opinions and Lifestyle Survey is relatively small, however, if clients require a larger sample size, multiple months of data can be merged together. The annual sample size of the Opinions and Lifestyle Survey is comparable with other Office for National Statistics (ONS) social surveys.

The Opinions and Lifestyle Survey has a maximum interview time limit of around 60 minutes each month. Generally, individual modules take between 1 and 10 minutes to complete. Therefore there is not the time to allow for in-depth probing on specific elements of the module subject that might be possible on other surveys. Questions included should be straightforward and directed to the majority of the population. The survey does not offer the facility to leave questionnaires or diaries with respondents to be posted back at a later date.

Timeliness and punctuality

(Timeliness refers to the lapse of time between publication and the period to which the data refer. Punctuality refers to the gap between planned and actual publication dates.)

The Opinions and Lifestyle Survey is carried out 12 times a year. The survey period lasts 14 weeks. This includes 4 weeks for developing and testing the questionnaire in BLAISE (a computer- assisted survey design and processing system), producing showcards when required and preparing derived variables. The survey is in the field for 4 weeks. After the data collection period, the data are cleaned, weighted, analysed and tabulated by the research team. Data and reports are sent to clients on an agreed date, approximately 5 weeks after the data collection period.

The Opinions and Lifestyle Survey provides data to clients with a rapid turnaround, but it is usually the responsibility of clients to further analyse and disseminate their findings. Occasionally the survey is commissioned to write reports or news releases. Previous examples include reports on smoking behaviour and contraception use.

For more details on related releases, the GOV.UK release calendar provides 12 months’ advanced notice of release dates. If there are any changes to the pre-announced release schedule, public attention will be drawn to the change and the reasons for the change will be explained fully at the same time, as set out in the Code of Practice for Official Statistics.

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6. How the output is created

The data are collected using face-to-face interviewing over a 4 week field period. The objective is to collect accurate relevant data on a survey with a quick turnaround, allowing clients to receive cleaned and processed data only 5 weeks after fieldwork. The population of interest is households in Great Britain and the achieved sample every month is around 1,100 interviews.

Sample design

A sample of 67 postcode sectors is selected each month. This is stratified by:

  • region
  • the proportion of households where the household reference person is in the National Statistics Socio-economic Classification (NS-SEC) categories 1 to 3 (that is, employees in large organisations, higher managerial occupations and higher professional employees or self-employed)
  • the proportion of households without a car
  • the proportion of people who are aged over 65

The postal sectors are selected with probability proportional to size and within each sector 30 addresses (delivery points) are selected randomly.

If an address contains more than one household, the interviewer uses a standard Office for National Statistics (ONS) procedure to randomly select which household to interview. Within households with more than one adult member, just one person aged 16 or over is selected with the use of a Kish Grid. The Kish Grid is a tool used to randomly select individuals in the household. It uses the address number and number of people aged over 16 in the household to randomly select the individual for interview. The interviewers endeavour to interview the selected person; proxy interviews are not conducted.

Weighting

Weighting factors are applied to Opinions and Lifestyle data to correct for unequal probability of selection caused by interviewing only one adult per household, or the restriction of the eligibility of the module to certain types of respondent.

The weighting system also adjusts for some non-response by calibrating the Opinions and Lifestyle sample to ONS population totals. Despite the considerable efforts made by interviewers to maximise response rates, approximately 35% of selected individuals decline to take part, or cannot be contacted. Differential non-response among main sub-groups in the population is especially problematic because this can result in biased estimates being produced and weighting can reduce this bias.

In order to compensate for differential non-response, the Opinions and Lifestyle sample is divided into weighting classes of age-group by sex and government region. The number of people belonging to each sub-group in the population is provided by ONS.

The weighting ensures that the weighted sample distribution across regions and across age-sex groups matches that of the population.

Consequently, respondents belonging to sub-groups that are prone to high levels of non-response are assigned higher weights. For example, young males living in London have a lower response rate and are therefore assigned higher weights than males living in other regions.

Weighting the data by age, sex and by region to estimate ONS population totals reduces the standard errors of survey estimates if the survey variable is correlated with age, sex and region.

Disclosure

Statistical disclosure control methodology is applied to the survey data. This ensures that information attributable to an individual or individual organisation is not identifiable in any published outputs. The Code of Practice for Official Statistics and specifically the Principle on Confidentiality set out practices for how we protect data from being disclosed. The Principle includes the statement that ONS outputs should “ensure that official statistics do not reveal the identity of an individual or organisation, or any private information relating to them, taking into account other relevant sources of information”. More information can be found in Confidentiality of data collected for statistical purposes.

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7. Validation and quality assurance

Accuracy

(The degree of closeness between an estimate and the true value.)

Sampling error

The Opinions and Lifestyle Survey is a sample survey, so estimates are subject to sampling variability. Sampling variability is dependent on several factors, including the size of the sample, clustering and the effect of weighting on the variable of interest. Standard errors, which give an indication as to the average amount that a given estimate may be expected to deviate from a true population value, are supplied for all main variables.

As discussed previously, the weighting process minimises the effects of non-response bias by accounting for the sampling process.

Non-sampling error

The Opinions and Lifestyle Survey is subject to non-sampling error including non-response. When an interview is not achieved in the field due to non-contact or refusal, the address can be re-issued to the telephone unit so that they can attempt to achieve the interview by telephone. This technique is estimated to increase the overall response rate by approximately 1.5%. The mean response rate for the period April 2011 to March 2012 was 62%.

Comparability and coherence

(Comparability is the degree to which data can be compared over time and domain, for example, geographic level. Coherence is the degree to which data that are derived from different sources or methods, but refer to the same topic, are similar.)

The classificatory questions and demographic questions that are asked at the beginning of every Opinions and Lifestyle Survey changed in April 2005. This change enabled harmonisation between core questions in the Opinions Survey and the Integrated Household Survey. Prior to April 2005 the Opinions Survey was conducted for 8 months of the year, with a monthly set sample of 3,000 addresses. From April 2005, the survey has been running for all 12 months, with a set sample of 2,010 addresses each month. Thus, caution is recommended in comparing data collected prior to April 2005 with data collected since April 2005.

The Opinions Survey was part of the Integrated Household Survey between January 2008 and December 2009, but this change did not affect the data that were deposited at the UK Data Archive.

The Opinions Survey is currently merging with the General Lifestyle Survey (GLF)5. To reflect this merger, from April 2012 the survey is now known as the Opinions and Lifestyle Survey (OPN). There has been no change to the survey methodology and so the data will be comparable with the data collected on the Opinions Survey.

It should be noted that comparisons with data previously collected on the General Lifestyle Survey may vary as the survey tool has changed. The General Lifestyle Survey was a household, annual survey with a slightly larger sample size than the Opinions and Lifestyle Survey, which is an individual monthly survey. After the first year of the Opinions and Lifestyle Survey, comparisons between the data collected on the two surveys can be compared and analysed.

There are a number of modules that have been running for a long period of time, for example, the tobacco module. This has run every month since 2001 and is deposited at the UK Data Archive. There is a discontinuity between the data collected prior to April 2005 and post-April 2005, due to the reason stated previously. The majority of modules run on the Opinions and Lifestyle Survey are one-off or run for a short period of time and would not be suitable for time series analysis.

The Opinions and Lifestyle Survey is made up of independent and often one-off modules, on topics that vary from month to month. We are therefore rarely able to make comparisons with other data sources.

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8. Concepts and definitions

(Concepts and definitions describe the legislation governing the output and a description of the classifications used in the output.)

National Statistics Socio-economic Classification

The National Statistics Socio-economic Classification (NS-SEC) replaces previous classifications that were based on social class and social and economic group.

Proxy response

The Opinions and Lifestyle Survey is different from other social surveys in that it does not collect proxy responses. This is due to the fact that a large proportion of questions asked on the survey are opinions questions, which are not suitable to be asked via proxy due to their subjective nature. Thus to avoid reducing the accuracy and quality of the data through adding a lot of missing or inaccurate responses, proxy responses are not accepted on the Opinions and Lifestyle Survey.

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9. Other information

Assessment of user needs and perceptions

(The processes for finding out about users and uses, and their views on the statistical products.)

As a forum to communicate with users but also as a means of obtaining information on users and uses, we ran the first Opinions and Lifestyle user day in March 2012 in which all users and clients of the data were invited to present findings and discuss their requirements and concerns. We endeavour to hold a user day annually.

As the survey is operated on a client-commissioned basis, we are in constant contact with users and their requirements are the primary driver for the survey’s content. Any changes to the survey are made in consultation with users and the potential effects on their data are considered.

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10. Sources for further information or advice

Accessibility and clarity

(Accessibility is the ease with which users are able to 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 release details, illustrations and accompanying advice.)

Statistical disclosure control methodology is also applied to data. This ensures that information attributable to an individual organisation is not disclosed in any publication. The Code of Practice for Official Statistics, and specifically Principle 5: Confidentiality, set out practices for how we protect data from being disclosed. The Principle includes a guarantee to survey respondents to ‘ensure that official statistics do not reveal the identity of an individual or organisation, or any private information relating to them’. More information can be found in National Statistician’s Guidance: Confidentiality of Official Statistics and also on the ONS Statistical Disclosure Control Methodology page.

Our recommended format for accessible content is a combination of HTML webpages for narrative, charts and graphs, with data being provided in usable formats such as CSV and Excel. Our website also offers users the option to download the narrative in PDF format. In some instances other software may be used, or may be available on request. Available formats for content published on our website but not produced by us, or referenced on our website but stored elsewhere, may vary. For further information please refer to the contact details at the beginning of this report.

For information regarding conditions of access to data, please refer to the following links:

Useful links

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Contact details for this Methodology