Table 3 Comparison of samples.

FB, Facebook.

Full sampleSample 2*Sample 3PSample 4§
% Democrat3132400.1740
Mean ideology (five-point)2.982.892.760.012.75
% Vote intention (Clinton)3637470.0747
% Voted in 2016 general0.590.590.630.010.63
% Knowledge (0–2)
Mean age5149490.1649
% High school or less2320220.1722
% Post to FB several times/day26280.2828
% Look at FB often65670.4268

*Column 2 summarizes characteristics of respondents who said in the survey that they have a Facebook account (i.e., they selected “Facebook” from the list of response options to the question “Do you have accounts on any of the following social media sites?”).

†Column 3 subsets to respondents (regardless of their answer in the previous question) who consented to share Facebook profile information with the researchers.

P values are computed from t tests of the difference in means between the sample of respondents who reported having a Facebook account and those who consented to provide access to their profile data.

§The final column subsets to those who shared any Facebook data at all that we were able to link back to the survey.