3
$\begingroup$

I know for sure that BMI(Body Mass Index) is a quantitative variable as it is a continuous variable. But is that BMI Category derived from the BMI a qualitative variable or a quantitative variable? (Underweight, Normal Weight, Overweight. Thanks

$\endgroup$
5
  • 1
    $\begingroup$ It is considered to be in this hybrid category called ordinal. Depending on what you’re doing, binning into these categories may discard useful information. What are you trying to do with BMI? $\endgroup$ – Dave Nov 10 '20 at 11:20
  • $\begingroup$ I am trying to make a contingency table with other categories, but I need to make sure that BMI Category is a quantitative variable. $\endgroup$ – Steven Steven Nov 10 '20 at 11:24
  • $\begingroup$ Why do you want to make such a contingency table ? What is your research question ? $\endgroup$ – Robert Long Nov 10 '20 at 11:39
  • $\begingroup$ I want to make a two-way contingency table with BMI Category and Favorite Ice Cream flavor to know if that a certain ice cream flavor can cause overweight. $\endgroup$ – Steven Steven Nov 10 '20 at 11:58
  • 1
    $\begingroup$ First, you can't establish causation with any kind of observational study. Second, why don't you use a regression model, with BMI as the outcome and ice cream flavour as the independent variable ? Categorising your data will lead to massive data loss. $\endgroup$ – Robert Long Nov 10 '20 at 15:52
7
$\begingroup$

Usually we think of this type of data as a special form of categorical data called "ordinal", that is, ordered-categorical. This is because there is a natural ordering in the data: Underweight < Normal < Overweight.

While it is sometimes useful to create categories such as these, there is a great loss of information by doing so.

Edit: Based on comments in the question, it would be a good idea to consider a regression based model, where you do not categorise BMI but rather use it as the outcome/response. Since you seem to have a just one independent variable, which is categorical, this would be a one-way ANOVA.

$\endgroup$
4
  • 1
    $\begingroup$ This ANOVA ends up being just a vanilla t-test! $\endgroup$ – Dave Nov 10 '20 at 19:09
  • $\begingroup$ @Dave but we don't know how many categories the IV has. Either way, it's better than categorizing the DV imho $\endgroup$ – Robert Long Nov 10 '20 at 20:10
  • $\begingroup$ I read the comment as being between two ice cream flavors. Looking at it again, I am not sure how. Yes, if there are 3+ flavors, then it isn't a t-test. $\endgroup$ – Dave Nov 10 '20 at 20:41
  • 1
    $\begingroup$ @Dave I agree it's a bit unclear but I think it's good as pedagogical device to think about regression. $\endgroup$ – Robert Long Nov 10 '20 at 21:18

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.