"Margin of error - The top portion of this graphic depicts probability densities that show the relative likelihood that the ""true"" percentage is in a particular area given a reported percentage of 50%.  The bottom portion shows the 95% confidence intervals (horizontal line segments), the corresponding margins of error (on the left), and sample sizes (on the right).  In other words, for each sample size, one is 95% confident that the ""true"" percentage is in the region indicated by the corresponding segment.  The larger the sample is, the smaller the margin of error is."