Online calculator which helps you solving the confidence interval.
Confidence probability shows the probability with which a random answer will fall into the confidence interval and is typically used 95%.
The confidence interval can be understood as an error which sets the scale part of the distribution curve on both sides from a point where we can get answers.
The formula assumes that for a given question there are two possible answers "Yes" or "no".
The more equal both answers and the closer the proportion is to 50/50, the larger the sample should be taken.
If the ratio is not known in advance, it is necessary to put 50%.