Scottish Climate Survey: technical report 2024 to 2025

In each selected household, up to two adults (aged 16 years or over) were invited to participate in the survey. In the interests of maximising the response rate, no selection criteria (other than being aged 16 years or over) were imposed regarding the selection of individuals within each household.

The estimate of the address level completion rate was based on those found in other recent surveys using a similar sequential online / postal mixed-mode design. The initial sample comprised 17,240 addresses, based on an assumed household response rate of 24.4%, and 1.3 online survey returns and 1 postal return per household (and 30% of responses overall comprising postal returns).

Three thousand addresses on the sample were randomly assigned to be part of a ‘soft launch’ – an initial pilot mailout of the first invite letter, a week in advance of the full mailout. This soft launch was to check if any amendments were required to different aspects of the survey administration, such as the letters, mailout process and the survey script, before the full mailout to the remaining addresses. The pilot raised no issues and no amendments were required.

Booster sample

Following the first four weeks of fieldwork, the number of completed surveys was lower than anticipated and at this stage a shortfall of between 400 and 950 surveys was estimated. Therefore, the decision was made to draw an additional ‘booster’ sample of 2,100 addresses.

The booster sample was targeted at addresses in the following four 6-fold urban/rural classification areas, due to a projected shortfall in these areas:

• Other Urban Areas (350 additional addresses)
• Accessible Small Towns (300 additional addresses)
• Remote Small Towns (850 additional addresses)
• Accessible Rural Areas (600 additional addresses).

Due to time constraints in the project timetable, the invitations to the addresses on the booster sample comprised two mailings (the households were not sent a reminder containing the postal version of the questionnaire):

• mailing 1: Initial invitation letter
• mailing 2: Reminder postcard

The first mailing took place six weeks after the start of fieldwork and the reminder postcards were sent one week after the first mailing.

In total, 19,340 households were invited to take part in the survey, including both the initial and booster samples.

Household sample design

At each address up to two adults were invited to take part in the survey. Two unique login codes for the online survey were provided on each invitation, and at the postal questionnaire mailing, one questionnaire was sent. Each adult who completed the questionnaire received their choice of a £5 online gift code or paper voucher.

Process for selecting adults within a household

There are many approaches that could have been used for selecting adults within households. For instance, the two adults with the most recent birthdays or the adults with the two next birthdays could be selected. These are commonly referred to as quasi-random approaches, as they are roughly equivalent to a fully random approach. While this would have randomised the selection process to a degree in households where there were more than two adults, in self-administered surveys it adds another barrier to completing the survey and has shown to not be carried out correctly in about 20% to 25% of cases.

With this in mind, it was decided not to apply any selection criteria for taking part in the survey. Instead, any two members of the household (aged 16 years or over) could take part.