No exact sample size can be mentioned here and it can vary in different research settings. For example if you test 100 samples of soil for evidence of acid rain your sample size is 100. The little letter for sample size mirrors other statistics such as x_i for the value of the variable X note big letter for member i in the sample.
If you have a subgroup sample size it is indexed so n_i for subgroup i.
N NX X N 1 where X Za22 p 1-p MOE2 and Za2 is the critical value of the Normal distribution at a2 for a confidence level of 95 a is 005 and the critical value is 196 MOE is the margin of error p is the sample proportion and N is the population size. If you have a small to moderate population and know all of the key values you should use the standard formula. Its called a sample because it only represents part of the group of people or target population whose opinions or behavior you care about. N sample size.