Regarding the Current Population Survey (from which the US unemployment rate is derived, among other stats).

"There are about 60,000 eligible households in the sample for this survey. This translates into approximately 110,000 individuals each month, a large sample compared to public opinion surveys, which usually cover fewer than 2,000 people. The CPS sample is selected so as to be representative of the entire population of the United States. In order to select the sample, all of the counties and independent cities in the country first are grouped into approximately 2,000 geographic areas (sampling units). The Census Bureau then designs and selects a sample of about 800 of these geographic areas to represent each state and the District of Columbia. The sample is a state-based design and reflects urban and rural areas, different types of industrial and farming areas, and the major geographic divisions of each state."

[bls.gov]

Have you got a link to the study. I’d like to check it out and the instruments they used to collect the data.

This poll was based on a sample size of 2,561 adults. I see a lot of polls with approximately the same sample size. I still fail to see how this is statistically significant when talking about representing over tens or hundreds of millions of people.

2,561 of 73,000,000 is approximately 0.0035%
[washingtonpost.com]