How to tell the difference between a discrete variable and a continuous variable

Descriptive statistics, The basics 14 Comments

In an introductory stats class, one of the first things you’ll learn is the difference between discrete and variable statistics. How to tell the difference between the two:

Step 1: Figure out how long it would take you to sit down and count out the possible value of your variable. For example, if your variable is “Temperature in Arizona,” how long would it take you to write every possible temperature? It would take you literally forever:

50°, 50.1°, 50.11°, 50.111°, 50.1111°, …

If you start counting now and never, ever, ever finish (i.e. the numbers go on and on until infinity), you have what’s called a continuous variable.

If your variable is “Number of Planets around a star,” then you can count all of the numbers out (there can’t be infinity planets). That is a discrete variable.

Step 2: Think about “hidden” numbers that you haven’t considered. For example: is time discrete or continuous? You might think it’s continuous (after all, time goes on forever, right?) but if we’re thinking about numbers on a wristwatch (or a stop watch), those numbers are limited by the numbers or number of decimal places that a manufacturer has decided to put into the watch. It’s unlikely that you’ll be given an ambiguous question like this in your elementary stats class but it’s worth thinking about!

Related posts:

  1. How to Classify a Variable as Quantitative or Qualitative
  2. How to Tell the Difference Between a Statistic and a Parameter
  3. How to Tell the Difference Between Different Sampling Methods
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14 Responses to “How to tell the difference between a discrete variable and a continuous variable”

  1. FHSV said:

    Sep 01, 09 at 7:35 am

    The link for “How to classify a variable as discrete or continuous” from the STA2023 FAQ goes to “How to Classify a Variable as Quantitative or Qualitative in Statistics.”

  2. Stephanie said:

    Sep 02, 09 at 3:11 am

    Thanks–the link is fixed :)

  3. Lida Cako said:

    Sep 04, 09 at 10:52 pm

    The article was helpful, especially in explaining the time question. There was a similar question in Chapter 1 homework, smth with 11 flashlights (sorry, I don’t remember word for word ) that involved time and I wasn’t sure if the correct answer was discrete or continuous.

  4. Stephanie said:

    Sep 05, 09 at 5:25 am

    Great, glad it helped!
    Stephanie

  5. Cathy Flanagan said:

    Sep 07, 09 at 2:38 pm

    This article was very helpful. I never thought to think of continuous pertaining to infinity, but that is probably why it is called continuous. I also like the time example. As first I thought it was continuous because I thought well time goes on forever, but there are only so many hours in a day.

  6. Sarah Joyner said:

    Sep 11, 09 at 2:03 pm

    When working in our books these variables threw me off a bit because sometimes they seemed to be both to me not one or other. This article is helpful in deciphering between the two.

  7. Philip Smith said:

    Sep 13, 09 at 9:03 am

    I think this article was helpful. I especially like the examples given and pointers on how to think about a problem. The concept still gets a little confusing, but I think with more practice I’ll get the hang of it.

  8. Hilary Dickert said:

    Sep 13, 09 at 3:32 pm

    I like the simplified way this article explains the difference between discrete and continuous. Yes, sometimes the contributing factors can be ambiguous, but at least your time examples give me a clearer way to correctly determine the answer. In other words, it’s easy to assume that statistics is a field that is all black and white. But this article proves otherwise. Thanks!

  9. Lisa Barcomb said:

    Sep 14, 09 at 5:44 pm

    This is the way to go to understand statistics. I like the way it is simplified and it explains everything you need to know on a level that you can understand. I like the examples that it gives and it breaks the information down. Because sometimes you get stuck and don’t know how to work a problem and this helps you out.

  10. Jennifer Thomas said:

    Sep 20, 09 at 12:08 pm

    This article was very helfpul in further explaining the difference between descrete and continuous.

  11. Stacey Bell said:

    Sep 22, 09 at 7:46 am

    Good article, I agree with the time example you would think on and on forever when in fact it does not go on it is limited.

  12. Joni Poore said:

    Jan 24, 10 at 7:56 pm

    When I was looking at this in the book, I was confused sometimes because (by prefernce) I thought it could be either. This explanation is a lot better formated, now to get to work with examples!

  13. Stephanie said:

    Jan 25, 10 at 7:51 am

    I’m glad these examples are helping you :)

  14. Vojta Bartak said:

    Apr 22, 11 at 3:20 am

    And what about geometrical distribution?!! It is discrete, but it takes infinite number of values… :-) I think simplification is not always a good way to understanding.

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