How should I decide on the sample size for a survey? That is a question often posed by survey researchers to statisticians. It is difficult to answer simply as in market research we carry out surveys which more often than not carry a large number of different questions. There may be questions which are more important than others and hence need to be answered with a higher level of precision. A good starting point therefore is to consider the most important item to be measured by a proposed survey. For the moment we will assume that the survey is to be carried out using a Simple Random Sample and that the survey result is a percentage.