You should not be running a poll if you do not know this.
1) 50 * (3/4) = 37.5 -- So 38 is the minimum requirement for a population of 50.
2) If there are more than 50 in the population, and you ask only 50, this is a "Sample" and it may take more than 38.
So, really, it depends on what you are doing and what you want to know, and how you want to know it.
Please hire a statistician before you publish dubious claims.