A 3% margin of error at a 90% level of confidence requires a sample size of about 750. For a 95% level of confidence, the sample size would be about 1,000.

Virtually always the reported margin of error assumes the maximum MOE for that sample size, ie, p = 0.5. It also nearly always assumes that a 95% confidence interval is being used.

Hold your breath and make sure you vote, because the result is likely to be a squeaker.

Learn about the confidence interval and why it's a useful metric for business operators, market researchers and investors alike.

And since pollsters generally use a confidence interval of 95 percent, one out of 20 polls will be a statistical outlier – that is, outside the margin of error – just by chance.