Over-Sampled?

Start your day with TPM.
Sign up for the Morning Memo newsletter

This evening everyone is chewing over the results of the latest sounding of the Democratic primary race provided by the new NBC/Wall Street Journal poll. A number of readers, questioning the results of the poll, have written in flagging this passage in NBC’s Chuck Todd’s analysis of the poll …

In addition, we oversampled African-Americans in order to get a more reliable cross-tab on many of the questions we asked in this poll regarding Sen. Barack Obama’s speech on race and overall response to last week’s Rev. Jeremiah Wright dustup.

Given Obama’s overwhelming support among African-American voters, if the poll had a disproportionately large number of African-Americans in its sample, that would definitely throw the results of the poll into question.

But I’m pretty sure that’s not what Todd is saying. What I think he means is this: In order to get a statistically reliable subset of African-American voters, they over-sampled this category. (Remember, African-Americans account for only about 13% of the US population. So that subset of a regular poll doesn’t really have a large enough sample to ensure a low margin of error.) They then re-weighted these results to come up with topline (everybody put together) numbers that adjusted for that oversampling.

Got that?

In any case, I don’t know that. But from my experience I’m pretty sure that’s what it means. I’d be very surprised if a major media outlet would release a poll like this without more clearly flagging that the numbers were skewed. In the meantime, we’ve shot off some emails to people involved with the poll to get confirmation one way or another. We’ll let you know what we hear.

Late Update
: A source at NBC confirms that this is correct. The results are weighted, as I described.

Latest Editors' Blog
Masthead Masthead
Founder & Editor-in-Chief:
Executive Editor:
Managing Editor:
Associate Editor:
Editor at Large:
General Counsel:
Publisher:
Head of Product:
Director of Technology:
Associate Publisher:
Front End Developer:
Senior Designer: