Sampling
The sample is the section of the wider population that will be engaged in the survey and sampling is the process of identifying who you will aim to contact from that population. The word ‘population’ is used to describe the target group, and while this may be the national population as a whole, it may also be a smaller group such as lone parents, or business members of a Chambers of Commerce in a particular location. Detailed consideration of sampling needs to be made to ensure the validity of your results, and the following issues need consideration:
Who is the respondent? The first thing you need to understand is who your respondent is going to be. This is the person that will provide the data you are asking for. If the survey is distributed among-st households, who in particular will be filling in the survey? Do you want to specify who the survey is to be completed by? And do you understand why you are specifying this person? The same is true when surveying organisations or groups. A survey will have much greater success if it is directed
to the right respondent. Identifying the person best suited to completing a survey will help to increase the response rate and generate more accurate data.
What is your sampling frame?
A sampling frame is a list of members of a population from which members of a sample are then selected. A sampling frame needs to be accurate, complete, up-to-date and relevant to the purposes of the survey for which it is to be used. Once you have an established sampling frame, depending on its size you may need to adopt a sampling technique to extract your final sample. For example random sampling, simple random sampling or stratified sampling (see further reading for more details on sampling techniques).
Are response rates likely to be a problem?
With any survey, you need to look at the profile of the people who did responded and satisfy yourself that they are about the same as the people who didn't respond – and also, that they’re about the same as the overall population that you’re sampling. If you send out a survey to a population, which is 50% male, and 50% female, but your responses are 80% from females then your findings will not represent your target population. Response rates can be low for surveys, under 20% for a postal survey is not uncommon. However, all the considerations in this section can help to improve your response rate.
Statistical significance: Understanding your population, sample size, and response rates are important for calculating 14 15 interval and confidence levels, which are vital in determining how many people you need to interview in order to get results that reflect the target population as precisely as needed. You can use online calculators to establish this type of information, but it is important to understand the terms and the reasons for doing this (see section on statistical analysis for more detail).