A 95% confidence level means that you would get the same results 95% of the time. 95% is the most commonly used confidence level but you may want a 90% or 99% confidence level depending on your survey. Decreasing your confidence level below 90% is not recommended.
https://www.surveymonkey.com/mp/sample-size/
The confidence level tells you how sure you can be. It is expressed as a percentage and represents how often the true percentage of the population who would pick an answer lies within the confidence interval. The 95% confidence level means you can be 95% certain; the 99% confidence level means you can be 99% certain. Most researchers use the 95% confidence level.
https://surveysystem.com/sscalc.htm
Necessary Sample Size = (Z-score)2 * StdDev*(1-StdDev) / (margin of error)2. Here is how the math works assuming you chose a 95% confidence level, .5 standard deviation, and a margin of error (confidence interval) of +/- 5%. ((1.96)2 x .5(.5)) / (.05)2. (3.8416 x .25) / .0025.
https://www.qualtrics.com/blog/determining-sample-size/
How well the sample represents the population is gauged by two important statistics – the survey’s margin of error and confidence level. They tell us how well the spoonfuls represent the entire pot. For example, a survey may have a margin of error of plus or minus 3 percent at a 95 percent level of confidence. These terms simply mean that if the survey were conducted 100 times, the data would be within a certain number of percentage points above or below the percentage reported in 95 of the 100 surveys.
https://www.isixsigma.com/tools-templates/sampling-data/margin-error-and-confidence-levels-made-simple/
By doubling the sample to 2,000, the margin of error only decreases from plus or minus 3 percent to plus or minus 2 percent. Although a 95 percent level of confidence is an industry standard, a 90 percent level may suffice in some instances.
https://www.isixsigma.com/tools-templates/sampling-data/margin-error-and-confidence-levels-made-simple/
*This sample size calculator uses a normal distribution (50%) to calculate your optimum sample size. The number of completed responses your survey receives is your sample size. It’s called a sample because it only represents part of the group of people (or population) whose opinions or behavior you care about.
https://www.surveymonkey.com/mp/sample-size-calculator/
Confidence Level. A confidence level tells you how reliable a measure is. Common standards used by researchers are 90%, 95%, and 99%. A 95% confidence level means if the same survey were to be repeated 100 times under the same conditions, 95 times out of 100 the measure would lie somewhere within the margin of error. When calculating your sample size, you'll use the z-score for your confidence level.
https://help.surveymonkey.com/articles/en_US/kb/How-many-respondents-do-I-need
A 5% margin of error would add 5% on either side of that number, meaning that actually 85-95% of your sample likes grape bubble gum. 5% is the most commonly used margin of error, but you may want anywhere from 1-10% for a margin of error depending on your survey.
https://www.surveymonkey.com/mp/sample-size/
) denotes its variance, then is an interval estimator of the parameter 9. The constant c is chosen in such a way that if the sampling process is repeated for a large number of times and for each sample an interval estimator is obtained, then approximately a pre-defined percentage of the intervals will enclose θ. This pre-defined percentage is known as ...
http://methods.sagepub.com/reference/encyclopedia-of-survey-research-methods/n87.xml
When you put the confidence level and the confidence interval together, you can say that you are 95% sure that the true percentage of the population is between 43% and 51%.
https://surveysystem.com/sscalc.htm
what is confidence level in survey
95% is the most commonly used confidence level but you may want a 90% or 99% confidence level depending on your survey.  