One of the first challenges in a natural disaster or humanitarian emergency is to obtain accurate estimates of affected populations (1). In the aftermath of rapid-onset disasters such as the recent tsunami disaster in south Asia, there is frequently an absence of adequate baseline data against which to measure the impact of the disaster. Available population data vary widely in quality, and the...

Power and sample size analysis or sample size determination is concerned with the question of determining the minimum number of samples necessary to demonstrate the existence (or absence) of a difference between two or more populations of interest. The number of samples should be sufficient in that the statistical test will reject the null hypothesis, when there really exists a difference, with...