Survey Analysis facts & stats

Question 1

A simple random sample of about how many people gives a margin of error of ±3 points?

Accepted Answer

1,067 cases. The margin for the gap between two candidates is roughly twice the margin for each one.

Question 2

Of 590 national polls, about how many would be expected to fall outside their margin of error purely by chance?

Accepted Answer

About 5% (roughly 30). The 590 were national presidential polls listed from Jan. 1, 2012, through the November election.

Question 3

In a 1,000-adult poll with a ±3 margin, what is the margin for a 200-person subsample?

Accepted Answer

plus or minus 6.9 percentage points. Pollsters usually report the margin at a 50% result, where it is largest.

Question 4

Below how many raw interviews will Pew not publish a subgroup estimate at all?

Accepted Answer

fewer than 100 raw interviews (or effective sample below 50). For subgroups of about 100 interviews, the margin of sampling error may reach 10 percentage points or more.

Survey Analysis facts & stats

Going deeper

A simple random sample of about how many people gives a margin of error of ±3 points?

In a 1,000-adult poll with a ±3 margin, what is the margin for a 200-person subsample?

Below how many raw interviews will Pew not publish a subgroup estimate at all?

Expert level

Of 590 national polls, about how many would be expected to fall outside their margin of error purely by chance?