MSNBC's Hardball again falsely suggested McCain holds statistically significant lead over Obama among white suburban women

Summary: Chris Matthews again aired an on-screen graphic that falsely suggested that Sen. John McCain's lead of 44 percent to 38 percent over Sen. Barack Obama among white suburban women in a recent NBC News/Wall Street Journal poll was statistically significant. A chart that appeared on-screen provided only the margin of error for the survey as a whole -- 3.1 percentage points -- and not the margin of error of 9.34 percentage points for the subset of white suburban women.

On the June 16 Hardball, MSNBC host Chris Matthews again aired an on-screen graphic, based on an NBC News/Wall Street Journal poll conducted June 6-9, that falsely suggested that Sen. John McCain's lead of 44 percent to 38 percent over Sen. Barack Obama among white suburban women was statistically significant. Specifically, a chart that appeared on-screen provided only the margin of error for the survey as a whole -- 3.1 percentage points -- and not the margin of error of 9.34 percentage points for the subset of white suburban women. Media Matters for America previously noted that on the June 12 edition of Hardball, Matthews aired two separate on-screen graphics based on the same survey that also falsely suggested McCain holds a statistically significant lead among the sample of white suburban women, without providing the actual margin of error for that subset.

While the chart was displayed, Matthews stated: "I want to start with some poll numbers here. The latest NBC News/Wall Street Journal poll has Senator Obama beating Senator McCain among women by 19 points, among white women by seven points. But McCain leads among suburban women by six." Matthews did not note that the margin of error for the subset of white suburban women was three times the 3.1-percentage-point margin of error for the poll as a whole, and the results for white suburban women highlighted on the chart were well within the margin of error and not statistically significant.

Huffington Post reporter Seth Colter Walls wrote on June 12 that after Huffington Post requested NBC's polling numbers on suburban women, "MSNBC has now provided The Huffington Post with more information on its 'suburban women' finding showing a 44-38 McCain lead over Obama. 'This is within the margin of error of 9.34 percent based on a sample size of 110 within the larger poll,' an MSNBC source wrote over email. (That's three times the margin of error for the entire poll.) This means McCain's 44 percent figure of support among suburban women could actually be as low as 35 percent, while Obama's 38 percent figure could rise as high as 47 percent -- assuming a 95 percent confidence interval (for the stat wonks in the house). Alternatively, McCain could be leading Obama 53-29. While those distant outcomes are less likely true than NBC-WSJ's 44-38 finding, that broad variance raises questions about the statistical usefulness of this one particular crosstab, as opposed to the rest of the NBC-WSJ poll on the whole."

From the June 16 edition of MSNBC's Hardball with Chris Matthews:

MATTHEWS: I want to start with some poll numbers here. The latest NBC News/Wall Street Journal poll has Senator Obama beating Senator McCain among women by 19 points, among white women by seven points. But McCain leads among suburban women by six. You first, Heidi [Harris, radio show host]. What way is this going?

HARRIS: Well, I think it's going to be interesting to see. And, to me, the biggest issue's gonna be, on the Election Day, how many people don't show up to the polls?

—E.H.H.