A survey of 15000 American adults in March 2011 found that 3

A survey of 15,000 American adults in March 2011 found that 35.3 % identify as Democrats and 34.0 % identify as Republicans, with the rest identifying as independent or other.

If we want 99% confidence, what are the margins of error in the estimate for the proportion of Democrats and for the proportion of Republicans?

Solution

n =15000

p of democrats = 35.3%

99% confidence interval z = 2.58

se2= p(1-p)/n

Margin of error = 2.58 (se)

Substituting all for the above we get

for democrats margin of error = 2.58 (se) =