Image 2: 483x178
The GRumbler

Introduction to The Group Rumbler ("GRumbler")

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

Update Notice: Users of Excel 2016 have reported some compatability issues with earlier versions of the GRumbler, with "Runtime Error 1004" appearing when launching the macro "Load Student Data into Search Engine". The GRumbler has been updated to take care of this issue, and a new version (January 2019) is posted below. The older version (January 2014) is retained and also available below, just in case users of older versions of Excel (either in the PC or MAC environment) have any trouble with the new "GRumbler.xlsm" file.

Please let me know of any other compatibility issues or error messages you encounter. Many thanks. (

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

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 by columnist Natalie Houston in the "ProfHacker" column she writes for the Chronicle of Higher Education. Read the ProfHacker articles here (3rd May 2011) and here (25th August 2011).

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).

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 the Excel file "GRumbler.xlsm" here. (Latest update: 10th January 2019)
(use "save" option, rather than "open")

Download the GRumbler Instructions file here. (Latest update: 10th January 2019)
("open" or "save" pdf file)

[If you are using older versions of Excel and prefer to stick with the previous (2014) version of the GRumbler,
that file is available here: "GRumbler.xls". This version was last updated: January 2014]

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




Copyright © 2011 The President and Fellows of Harvard College