送交者: HunHunSheng 于 2005-4-05, 15:30:43:
回答: Why US polls always have a margin of error of +/- 3% ? 由 乱劈材 于 2005-4-05, 14:32:46:
and assume 50%-%50% split.
When the sampel size is big enough, you can
always assume normal distribution by
invoking cnetral limit theorem