In statistics the sample size is the number of subjects that make up the sample drawn from a population, necessary for the data obtained are representative of the population.
Terminology sample size

1. Level of confianza.- confidence level tells you how “safe” may be that your population select certain response.
2. confianza.- Interval The confidence interval is the +/- range that is added to the answer you receive from your sample to provide a percentage range that accurately describes the likely response of the population.
3. The higher population.- sample is compared to the total population, the more accurate the answers. However, if the population is too large or is unknown, you may leave this information blank, as in mathematical terms the differences are statistically minimal.
4. muestra.- size Sample size is the largest fragment within a population that you have chosen for the survey people. The higher the sample compared with the total population, the more accurate the responses.
   For example, if you perform a sample of 1,000 people with a confidence level of 95% and a confidence interval of 3, and 70% choose Brand A, you may have a 95% certainty that between 67% and 73% (70% +/- 3) choose Brand A.
   In this application we can consider the heterogeneity p value equal, ie if we place the value of heterogeneity equals the value 0.5 0.5 p and q will be 0.5, and p and q must add 1.