2020 Treasure State (Montana) Election Surveys

The Treasure State 2020 Pre-Election Survey was conducted by the HELPS Lab of Montana State University-Bozeman between September 14 and October 2, 2020. The original population for the survey was Montana voters who registered by August 20, 2020, and were deemed active by the Montana Secretary of State. We stratified the sample by state house districts, and then drew a random sample of 9,000 voters proportionally from these strata. Sampled individuals received a questionnaire by mail and were asked to return the questionnaire via a prepaid business reply envelope. Respondents returned 1,789 surveys, a response rate of 20.2% based on 8,836 deliverable addresses. The Treasure State 2020 Post-Election Survey, also conducted by the HELPS Lab, used a panel design that returned to the individuals who responded to the Pre-Election Survey. This survey was in the field from November 4-25, 2020. Of the 1,789 original respondents, 1,069 completed the post-election questionnaire, for a response rate of 59.8%. The procedures for the Post-Election Survey otherwise paralleled those for the Pre-Election Survey.

The number of individuals voting in the 2020 general election in Montana was 612,075, according to information from the Montana Secretary of State. We have adjusted the overall survey margin of error (MoE) for design effect owing to our subsequent use of weights in calculating results. This adjustment has the consequence of making the margin of error substantially larger than it otherwise would be. For the pre-election sample, this results in a MoE of +/- 3.7 percentage points, using a confidence level of 95% and a response distribution of 50% (the most conservative estimate) with the given population size. For the post-election sample, the corresponding MoE is +/- 6.0 percentage points. We note that these figures are overall approximations given sampling stratification and different response options and response patterns for specific questions.