Strategy Survival Guide
Strategy Survival Guide
Strategy Survival Guide
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• The "population" and “sub-groups” to be studied: the sample to be surveyed needs to be carefully<br />
selected to ensure that the findings are similar to those found amongst your target population. There<br />
are three basic types of sampling:<br />
1. Probability sampling. This includes random sampling, systematic sampling (similar to<br />
random sampling but some element of selection e.g. every 100th person in directory), and<br />
cluster sampling (e.g. pupils in a particular school). Consideration needs to be given to the<br />
'sampling frame’ – such as the voting register, telephone book etc. If the sampling frame is<br />
biased, such as richer people being ex-directory or poorer people avoiding the voting<br />
register, then this problem will be reflected in the sample.<br />
2. Non-probability sampling. This can be useful when there is insufficient information about the<br />
population (i.e. there is uncertainty about how many people or events make up the<br />
population) or the population is intrinsically difficult to survey e.g. the homeless. Non<br />
probability sampling techniques include purposive sampling (e.g. the sample is handpicked)<br />
or snowballing (those identified for inclusion in the sample nominate others). Caution must<br />
be taken in generalising from such samples.<br />
3. Stratified sampling. This involves dividing the sampling frame into segments and 'oversampling’<br />
sections of the population. For example, a survey might deliberately over-sample<br />
young people or ethnic minorities in order to ensure that there are sufficient in the sample to<br />
make reliable statistical comparisons. Such samples can be 're-weighted’ to give averages<br />
that are representative of the whole population. Stratified sampling is usually necessary for<br />
sub group analysis.<br />
• Optimum sample size: the sample size needs to be an adequate size, in order to generalise from the<br />
survey's findings. Provided that the sample size is representative of the target population, the larger<br />
the sample size, the more confident you can be that the results are an accurate reflection of the<br />
population as a whole. The key factor is the absolute size of the sample, rather than the proportion of<br />
the population that gets included in the sample. Adequate samples can be estimated from the<br />
expected variation in the major variables of interest, and will therefore depend on the specific<br />
question or hypothesis to be tested. As a general rule of thumb, adequate samples will generally<br />
involve more than 30 events or people. Most market research companies use samples of around<br />
1000-2000. However, other factors to consider when deciding on the sample size include the likely<br />
response rate, the desired level of accuracy, sub-divisions in the data etc. For example, if the survey<br />
seeks to discover not only the general attitude towards an issue, but also that of married men under<br />
40, single parents etc, then a larger sample will be needed. Advice from a statistician or social<br />
researcher will help to ensure that the chosen sample size will yield reliable and relevant data.<br />
• Data collection method: there are a variety of different methods for actually collecting survey data.<br />
Each has pros and cons:<br />
1. self-completion postal questionnaires: this can be expensive and the typically low response<br />
rates, can result is a selection bias and hence doubt in the validity of the findings.<br />
2. face to face interviews: market researchers may approach people in the street, or call at<br />
people’s homes. On other occasions contact will be made in advance by phone or letter.<br />
Response rate is usually higher than for postal surveys but face to face interviews tend to be<br />
more expensive. Decisions will need to be made about whether the interviews are to be<br />
structured, unstructured or partially structured.<br />
3. telephone interviews: these are quicker and cheaper than face to face interviews, but have<br />
the highest non-response rate because people are less inhibited about saying no over the<br />
phone.<br />
Checklist for Designing a Survey or Questionnaire<br />
1. Wording of the questions:<br />
• Style of question should be suited to target group e.g. children or professionals. The table below<br />
provides some alternative styles.<br />
• Respondents should only be required to answer about themselves, not others<br />
• Avoid the use of leading questions<br />
<strong>Strategy</strong> <strong>Survival</strong> <strong>Guide</strong> – <strong>Strategy</strong> Skills<br />
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