The GRumbler

Introduction to The Group Rumbler ("GRumbler")

The GRumbler and Instruction files are available here (see below) for free download.

Happy GRumblers: 

15th July 2020: Becky Hlavac, M.S., Instructor and Lab Coordinator, Clinical Anatomy, Arizona School of Health Sciences, wrote:
"Our online anatomy course began this week, and we distributed a pre-course survey to the students. I used the data from the pre-course survey to determine the "conflicts" for the GRumbler, and it worked absolutely beautifully. We have 130 students in our class, and using the GRumbler, putting them into equally diversified groups took all of five minutes. I am immensely grateful to have found such a powerful tool - thank you so much again for putting it out there."

[Note: If you'd like to be featured on this site as our latest "Happy GRumbler", please e-mail me, noting how you would like to be identified.]

Background: Malcolm Sparrow created The GRumbler to help with the frustratingly complex (and inherently mathematical) task of dividing classes of students into small groups for the purposes of group discussions, exercises, or project work--groups which are simultaneously balanced in terms of gender, nationality, experience, or job description (or in terms of any other factors or criteria that course administrators deem important, and around which they want to guarantee optimal mixing).

The GRumbler was first released in January 2011, and has been featured twice (on 3rd May 2011 and 25th August 2011) by columnist Natalie Houston in the "ProfHacker" column she writes for the Chronicle of Higher Education.

The GRumbler is now used quite broadly at the Harvard Kennedy School for a range of group-assignment tasks:

  • To create study groups for Executive Programs
  • To divide participants at major conferences into subgroups for break-out sessions
  • To assign degree program students across multiple sections of major courses
  • To assign degree program students to project teams for major exercises
  • To create sequences of team assignments in negotiations courses, to guarantee that students work with different partners for each successive exercise.

The GRumbler is designed to maximize the mixing across the class and provide the greatest possible degree of diversity within each group. The GRumbler can also generate sequences of up to 50 successive group assignments, for use on different days or for different exercises, that have minimal overlap with one another (i.e. that keep students apart who have been together in any group before).

Instructional video: A short and very useful video, created by Brian Moynihan of UNC's School of Medicine, is available on YouTube here.

To try the GRumbler for yourself: First download the following two files to your own computer. Please make sure you download and use the latest (and therefore the fastest and most bug-free) versions. 

Download a zipped version of the Excel file "GRumbler.xlsm" here. (Latest update: 11th October 2021)
(use "save" option, rather than "open", and then unzip. Make sure that the files are downloaded to your own physical hard drive, rather than to a shared network location or the Cloud, as rights controls for networked locations may limit the ability of the GRumbler to create and write files).

Download the GRumbler Instructions file here. (Latest update: 11th October 2021)
("open" or "save" pdf file)

[If you are using older versions of Excel and cannot use xlsm files, an xls version of the GRumbler is available here: "GRumbler.xls".]

Then I would recommend you print out the Instructions, and have them alongside as you experiment with the GRumbler. The Instructions file includes a tutorial that leads you through a demonstration, using data about a fictional class of 49 students which is already included within the GRumbler file when you first open it. The tutorial should take less than an hour to work through, and shows all the basic operations of the GRumbler's group-assignment process. The tutorial explains how to clean the fictional student data out of the GRumbler and start working on your own data as soon as you have finished with the demonstration.

The instructions file also contains (towards the end) a section of Frequently Asked Questions.

I hope the hour or so you may spend up front learning to use the GRumbler will pay off handsomely over time. The people who will appreciate the GRumbler most of all will be those who previously spent many frustrating hours shuffling color-coded index cards around on large tables, trying to create balanced and non-duplicative sequences of group assignments. You will already know, for sure, if you are such a person!

Happy GRumbling.

Malcolm Sparrow


Latest Update Notices:

Update Notice for MAC users (August 2019): MAC users, using MAC OFFICE 2016 (or later) have recently reported some compatability issues with earlier versions of the GRumbler, with error messages appearing when launching the macro "Prepare Group Lists and Master List," which is used to create "Results" files. The reasons for this include (a) changes in the filename delineators used within MAC Office versions 16.xx and later, (b) changes in "fileformat type" specifications for MAC OFFICE implementation in 2011 (versions 14.xx) and 2016 (versions 15.xx), and (c) introduction of "Sandbox" controls for MAC OFFICE 2016 which restrict which parts of a user's directory structure can be accessed automatically.

The GRumbler, and the GRumbler instructions file, have been updated to take care of these issues, and new versions (August 2019) posted above. None of these changes will affect PC users.

Users of MAC OFFICE 2016 (versions 16.xx and later), when launching the macro to create a results file, may still encounter additional pop-up dialog boxes asking for your permission to access a specific directory on your machine. Whether or not these dialogs appear depends on where, within the directory structure, the GRumbler.xlsm file is located. If they do appear, simply grant the necessary permission, and the results file should then be created in the normal way.

Please let me know of any compatibility issues or error messages you encounter, along with the specs for your Operating System and Excel/Office version numbers. Many thanks. (