Here's an example of what I was talking about with respect to people making a big deal about changes in poll results from week to week; as though they are looking at an exact measurement of the reality:
Yesterday IPSOS polling posted an article containing this Statement:
The general election race has narrowed between Donald Trump and Hillary Clinton. Clinton (41%) continues to lead Trump (37%) among registered voters, but the Democrat has lost ground since last week
http://www.ipsos-na.com/news-polls/pres ... px?id=7240
On May 5 IPSOS referenced the situation described as "last week" as follows:
In hypothetical 2-way general election matchups between Donald Trump and Hillary Clinton, the Democrat (45%) continues to lead the Republican (36%) solidly (+9) among registered voters.
http://www.ipsos-na.com/news-polls/pres ... px?id=7230
Even if the poll had been conducted with perfect, theoretically sound probability sampling the difference between results from the two weeks could easily be due to random sampling error. And pollsters can't get perfect, theoretically sound samples. I think they do a remarkable job of adjusting for that. But it does mean there's going to be some non-sampling error. It just drives me crazy that people will NOT restrain themselves and instead act like results like the May 5 and May 9 IPSOS estimates provide sufficient evidence to conclude there was a change when they don't. And it's particularly bad that the the polling site itself does that because they should know better. I also think doing that actually influences peoples' opinions. Not as bad this far out but doing something like that close to an election could even cause people to decide to vote or not vote.
BTW the referenced polls are IPSOS on line polls; which are graded C+ according to
http://fivethirtyeight.com/interactives ... r-ratings/ . Interesting that IPSOS telephone polling is rated A-. For your information, in general, telephone polling which includes both land line and cell phone calling is considered to be the best data-gathering method by the people responsible for the ratings site. At least as of the date when the ratings were posted...which admittedly was in 2014...IPSOS on line polling was characterized by a slight bias in favor of the Republican candidate. In other words the suggestion was that it tended to over estimate how well the Republican was doing.