methodology for trump support

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METHODOLOGY

The July 20-26, 2015 NBC News online survey was conducted by SurveyMonkey among a national

sample of 8,228 adults aged 18 and over. The August 7-10, 2015 NBC News online survey reported in

this article was conducted by SurveyMonkey among a national sample of 9,127 adults aged 18 and over.

Respondents for each of these non-probability surveys were selected from the nearly three million

people who take surveys on the SurveyMonkey platform each day.

Data for each survey have been weighted for age, race, sex, education, and region using the Census

BureausAmerican Community Surveyto reflect the demographic composition of the United States.

Because the sample is based on those who initially self-selected for participation rather than a

probability sample, no estimates of sampling error can be calculated. All surveys may be subject to

multiple sources of error, including, but not limited to sampling error, coverage error, and measurement

error.

To assess the variability in the estimates and account for design effects, we create a bootstrap

confidence interval, meaning we use the weighted data to generate 1000 independent samples and

calculate the standard deviation of the weighted average using those samples, producing an errorestimate.

When analyzing the survey results and their accuracy, this error estimate should be taken into

consideration in much the same way that analysis of probability polls takes into account the margin of

sampling error. For example, if 47 percent of voters say they support Candidate A and 43 percent of

voters support Candidate B, and the error estimate is plus or minus 3.5 percentage points, Candidate A

could be supported by as low as 44 percent of voters and Candidate B could have as high as 47 percent

of support. Therefore, Candidate A does not have a "lead."

The following tables provide the unweighted sample sizes and the error estimates that have been

calculated in place of the margin of sampling error for a variable that is expected to have close to an

even split in most groupings (such as gender):

July 20-26, 2015 NBC News online survey

Group Unweighted N Plus or minus

Total sample 8,228 1.6 percentage points

Republican RVs 3,060 2.7 percentage points

Democrat RVs 3,341 2.6 percentage points

18-29 1,082 4.1 percentage points



65+ 1,382 3.9 percentage points

White 6,628 1.8 percentage points

Black 586 5.8 percentage points

Hispanic 428 6.1 percentage points

Other 490 6.3 percentage points

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August 7-10, 2015 NBC News online survey

Group Unweighted N Plus or minus

Total sample 9,127 1.5 percentage points

Republican RVs 3,991 2.2 percentage points

Democrat RVs 3,214 2.6 percentage points




65+ 1,730 3.2 percentage points

White 7,375 1.5 percentage points

Black 566 5.2 percentage points

Hispanic 453 5.9 percentage points

Other 733 4.9 percentage points

Omitted table from the article:

Average - Non -Trump

Republicans

Average -Trump

Republicans

Difference inAverages (Trump

Republicans -Non-TrumpRepublicans)

Female 47% 41% -6

High school education or less 34% 43% 9

Age: 18-24 9% 6% -3

Age: 65+ 23% 24% 1

Under $50k 27% 31% 4

$100k+ 31% 28% -3

White 82% 87% 5

Self-identified very conservative 19% 21% -2

Evangelical 46% 37% -9

Religious attendance - at least once/week 46% 32% -14

Sample size (N)

3,719(unweighted)

932(unweighted)

methodology for trump support

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