Margin of error tells you how much error surrounds a measure. It's a percentage that describes how much the opinions and behavior of the sample you survey is likely to deviate from the total population. To calculate your margin of error, use our margin of error calculator.
The smaller the margin of error is, the closer you are to having the exact answer at a given confidence level.
In general, the larger your sample size, the lower the margin of error. The closer your sample is in size to your population, the more representative your results are likely to be. And that’s why you’ll notice that the recommended sample size in the table below gets smaller as your tolerance for error gets larger.
For example, let's say we asked 400 people if they have a favorable or unfavorable opinion of Barack Obama and 55% say favorable. Using a 95% confidence level and ±5% margin of error, if we repeated this survey 100 times under the same conditions, 95 out of 100 times, the response would be somewhere between 50% and 60%.
