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NBC News Online Poll: Public Opinion on the Boston Marathon Bombing Embargoed for release after 4:00 PM Wednesday, April 8, 2015 TOPLINES Questions 1-13 and 18-34 held for future release. 14. How likely do you think it is that there will be a terrorist attack in the United States within the next few months? Very likely Somewhat likely Not too likely Not at all likely DK/NA 4.6-8.15 8 38 40 12 1

15. In general, how well do you think the U.S. government is doing in reducing the threat of terrorism: very well, somewhat well, not too well, or not at all well? Very well Somewhat well Not too well Not at all well DK/NA 4.6-8.15 13 49 26 11 1

16. How closely have you been following the trial of the Boston Marathon bombing suspect Dzhokhar Tsarnaev: Very closely Somewhat closely Not too closely Not at all DK/NA 4.6-8.15 5 30 40 25 1

17. As you may know, Dzhokhar Tsarnaev faces a 30-count indictment stemming from the bombing of the 2013 Boston Marathon. Which punishment would you prefer for Tsarnaev if he is found guilty: [ROTATE RESPONSES]

The death penalty Life in prison with

no chance of parole Not sure* DK/NA 4.6-8.15 47 42 11 1

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METHODOLOGY

The NBC News Online Poll was conducted online by SurveyMonkey April 6-8, 2015 among a national sample of 2,052 adults aged 18 and over. Respondents for this non-probability survey were selected from among those who have volunteered to participate in the SurveyMonkey Contribute panel. This SurveyMonkey Audience project was run using a balanced sample. The process of sample balancing starts by setting targets for desired numbers of completed responses among certain groups (in this case: by gender, age, and race groupings). After that, a specified number of potential respondents are allocated to the project based on expected completion rates. Panelists are either linked directly to the survey from an email invitation, or routed to the survey after agreeing to take an additional survey after completing a prior one. Once the survey is put into the field, the system calculates actual completion rates by group, and uses that information to re-adjust the flow of new panelists to the survey. SurveyMonkey panelists are emailed no more than once every three days, and on average panelists receive one email every two weeks. SurveyMonkey also imposes a daily limit on the number of surveys a panelist can take. Data for this survey have been weighted for age, race, sex, education and region using the Census Bureaus American Community Survey, along with data from the Kaiser Health Tracking Poll on evangelicalism to 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 and polls 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 error estimate. 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 table provides the unweighted sample sizes and the error estimate that has 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 (gender):

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Group Unweighted N Plus or minus

Total sample 2052 3.0 percentage points

Republican 424 6.3 percentage points

Democrat 798 4.7 percentage points

Independent 796 4.6 percentage points

18-29 315 7.5 percentage points

30-44 376 6.2 percentage points

45-59 754 4.5 percentage points

60+ 607 5.3 percentage points

White 1383 3.8 percentage points

Black 204 9.0 percentage points

Hispanic 317 7.2 percentage points

Other 148 12.3 percentage points