Under: Opinion polls
19 Oct 2016


Now I know that this is not the most interesting subject but I had of dose of this in college statistics classes (3) for my undergrad and graduate degree. In business, statistics are mostly used for continuous process improvement or validating supply and product variances. But I would dare to say that the way most of us know about polling is during the political seasons. :(


In this article I will give an overview of opinion polls and the parts that might make a difference in determining accuracy. While I am no expert, I have been exposed and understand the concepts. I will have one really good link that will explain this very well and three videos that are nice visual aids.


One of my pet peeves with opinion polling is that the confidence interval is not published as the sample size and margin of error. Typically one can have anywhere from 90% to 99% confidence interval – a huge difference this can be as important or more important than the margin of error! And this information is not easily available. But the media perpetuates the myth that the margin of error is the only (or certainly implies it is the main) factor to look for in polling data.


Here are the parts of a sample:

  • Survey questions
    • not too complex
    • not bias
  • Methods to reach sample population
    • landline phone
    • mobile phone
    • in person
    • via internet

  • Random survey of sample population
    • you cannot select the people – that is not random (for instance all subscribers of a liberal newspaper)
    • does it include ethnic, religious, young, middle aged, old, and other variances in the population?
    • If it is not random or not representative of the population – it is not valid (sample error)
  • Margin of error
    • How likely your samples will answer how you predict in the range
    • a +/- 3% margin of error has a 6 point range that likely can overlap with some of the other candidates
  • Confidence interval
    • How confident your survey results range will be be as predicted
    • a 90% confidence interval says that 10% of the time – the results can fall outside of the margin of error


Here is an good article entitled, “Why polls can be wrong…” and below are the videos if you like your information delivered audio/visually.




Here is a pros and cons of opinion polls.



The last video talks about confidence intervals.



I hope you have enjoyed this overview of statistical polling. Now keep the faith for your favorite candidates because the polls may not predict the outcome.

If you enjoyed this post, make sure you subscribe to my RSS feed!

4 Responses to “Opinion Polls; How Accurate are they Really?”

  1. Dr. J Says:

    I’ve never liked polls. I guess we will find out it nineteen days how accurate they have been. Do you think the newspapers need to have two front page headlines ready just in case :-)

  2. John W. Zimmer Says:

    :) I’m just so glad someone will finally win. In CA we have 17 state wide propositions to try and figure out and always the smaller races and judges. The citizens have way too much work to do this time. :(

    That was funny reading about how Dewy beat Truman in the morning paper (they depended on polls) :)

  3. Dr. J Says:

    You were very prophetic with this, John, as history has now shown!
    I recently watched a news segment on Fox where they interviewed Stony Brook University Political Science Professor Helmut Norpoth. He had predicted a Trump win in February and he explained how he did it and why the pollsters were wrong.

  4. John W. Zimmer Says:

    I had a feeling when the polls were close to the margin of error and he (Trumph) was drawing huge crowds… so polling is as much as an art as it is a science. :)