Ballot Lead Calculator

	American Research Group, Inc.

Does one candidate really have a lead over the other?

The theoretical margins of error provided for most polls do not take into consideration the sampling error for the difference between two estimates that are derived from the same sample. This sampling error is larger than the margins of error for single estimates. Use this calculator to determine if one candidate has a lead over the other based on the results from a poll.

Enter the ballot numbers for the candidates in the poll and then enter the sample size for the poll. Click on the "Calculate Limits" button to determine the lower and upper limits of the confidence interval for the difference in the ballot numbers (at the 95% confidence level).

Candidate A		%
Candidate B		%
Sample size
Upper limit
Lower limit

If the lower limit is 0 or less (a negative number), there is no significant difference between the ballot numbers for candidates A and B - they are statistically tied in that poll.

If the lower limit is greater than 0 (a positive number), there is a significant difference between the ballot numbers and the leading candidate has a statistically significant lead over his opponent in that poll.

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