Quick Simultaneous Confidence Intervals for Multinomial Proportions.

Opinion polls often give an indication of sampling error based on the standard conservative confidence intervals for a single binomial proportion. We give a lower bound for the simultaneous coverage probability when such intervals are applied to all of the proportions in a poll. This bound is equal to 1 - 2 alpha for small values of a. The same result is shown to apply to the standard confidence intervals for changes in proportions between surveys. [ABSTRACT FROM AUTHOR]