How small errors can have a big impact on small populations

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When you checked the boxes on your census form, you probably did not pay much attention to the form design. But it is something the Census Bureau researches and gives a lot of attention. Something as simple as using vertical instead of horizontal boxes can have a big impact on how you read the form and the data we gather.

If one person’s eye misreads the form and checks the wrong box, it may not change percentages of statistics very much. But if even 1 percent of a large population checks the wrong box on a question, it could lead to an inaccurate picture of a smaller population.

For example, you’ll see in the video below that if you have 1,000 circles and 100,000 squares and just one-percent of the squares are counted as circles, then that’s one thousand squares now listed as circles. This mismarking would result in responses that double the amount of circles.

A similar data capture error affected the 2010 Census results for same-sex couple households. On the form used by census takers, the boxes for sex were placed vertically, and the wrong gender box was marked for a small percentage of opposite-sex partners, artificially increasing the percentage of same-sex couple households.

When we discovered this inconsistency in the responses, we developed a better set of estimates to provide a more accurate measure of same-sex married and unmarried partner households. These estimates are now available.

At the Census Bureau, we strive to eliminate these kinds of errors and modify our survey questionnaires to gather the best possible data on the nation’s people, places and economy.

This brief video illustrates how a small error in a large population can create a large error in a smaller related population, such as the same-sex couple population.

For more information, visit our online press kit.

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6 Responses to How small errors can have a big impact on small populations

  1. David Bee says:

    Let’s hope the Bureau eliminates English errors too:
    “This mismarking would result in responses that double the amount of circles.”
    Note: No reason to post this — simply correct it!

  2. David Bee says:

    You should correct this gem of English:
    “This mismarking would result in responses that double the amount of circles.”

  3. David Bee says:

    Hmmm…thought this five-point question from a recent exam of mine would supplement the previous Comments well:
    3. For each of the following, determine whether discrete-type (D) or continuous-type (C) numerical data result from it. (Circle D or C.)
    (a) Time: D C
    (b) Rate of speed: D C
    (c) Number of persons: D C
    (d) Amount of something: D C
    (e) Number of something: D C
    Now, it would be hard to believe someone at the Bureau
    would consider the answer to Part (d) to be D, but, unfortunately, that’s just what the sentence “This mismarking would result in responses that double the amount of circles” indicates…

  4. Markey says:

    Despite David’s Beeeerilliance, he has taken three comments to do nothing constructive and has yet to provide his version of a correct sentence. Too hard to make a correction, David, or perhaps you are one of those who prefer to complain instead of contributing??

  5. David Bee says:

    Markey:
    First things first: If such were corrected by someone at the Bureau after the first comment, then there would be no need for Comments Two and Three.
    My version of The correct sentence? Simply, This mismarking would result in responses that double the number of circles.
    Wrt Markey’s claiming I “prefer to complain instead of contribut[e]”, I did contribute by bringing attention to the error, which unfortunately no one corrected. (I find it hard to believe, Markey, that someone on this blog of the Census Bureau , perhaps the finest public scientific sampling agency in the world, doesn’t know the difference between amount and number…)

  6. David Bee says:

    Earlier this/last week a sentence on the NYTimes Website was corrected to read as follows:
    “With the new focus on conference matchups, the Rangers, for example, will play the Bruins the same number of times they play the Sharks (twice).”
    The original sentence had “amount” instead of number and after a Comment was sent pointing such out, the Editor corrected such sans posting the Comment.
    Thus, simply, why wasn’t the same done here instead of having the five previous comments — as well as this one — posted?!

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