What should my Sample Size be?

Sample Size, as explained by DJS Research Ltd.

A sample is the number of consumers or respondents that you research. The number is decided by the specific aims you are trying to achieve through the particular study and can therefore vary somewhat. The research must be valid statistically and also reliable (or else it would be pointless undertaking the project), therefore the sample size should reflect the degree of accuracy that you are looking to achieve. In addition it needs to consider the size of the respondent group which you’ve targeted, the number of smaller sub-groups within that group, and also the cost of interviewing or researching a set number of people – more people means more expense.