Sampling If a sample is to be selected, decide on the sampling procedure for getting an unbiased, representative sample. Avoid self-selection, that is volunteers who come forward with information and answers. There is no need to use large numbers for a prevalence survey on tobacco use. Large numbers are generally required in surveys on the association between tobacco use and diseases. One way of determining sample size is the desired precision of the estimate of prevalence in the smallest sub-group.
Sample size depends a lot on the resources and other practical considerations.
Depending on the objectives it would be desirable to include other items of information such as indicators of socio-economic status, reasons for starting the tobacco use, perceived association with diseases, attitude towards tobacco control measures, attempts at quitting the habit, etc. Use international standardized criteria, e.g. those given by the WHO and the UICC as far as possible. The last method may be the only valid option if part of the population is illiterate. Pretest the proposed methodology in a pilot survey on a small sample. Reduce it as much as possible, for example, by sending reminders, changing the time of the interview, repeating the visits etc.