Introduction Sample size calculation is an integral part in the inferential statistics, in which we are estimating a population parameter (our interest) from a sample statistic (data available to us). We carry out experiment on a finite numbered sample and calculate a summary measure out of it (sample statistic, lets say, sample mean) with an intent to estimate the unknown population parameter (population mean).
The basic premise of statistical estimation is that as the sample size increases, the sample statistic will be reflecting the population parameter more accurately (its variation will be less around the population parameter).