A much smaller proportion of the polls than expected produce confidence intervals containing p. If you look closely at the table, you will see that most polls that fail to include p are...

A much smaller proportion of the polls than expected produce confidence intervals containing p. If you look closely at the table, you will see that most polls that fail to include p are underestimating. The reason for this is undecided voters, individuals polled that do not yet know who they will vote for or do not want to say. Because, historically, undecideds divide evenly between the two main candidates on election day, it is more informative to estimate the spread or the difference between the proportion of two candidates d, which in this election was 0.482 − 0.461 = 0.021. Assume that there are only two parties and that d = 2p − 1, define:

and re-do exercise 1, but for the difference.