5 August 2014

Deliberate Mistakes

Image: weandserendipity.com
I'm always on the lookout for new ideas for GCSE revision lessons. If I write about this idea now then hopefully I'll remember it come Spring.

This year I had great success with relay races and carousels in my revision lessons. I also did some pupil-led lessons which were a lot less successful.

This 'deliberate mistakes' idea is something I've adapted from this blog post, so thank you to @bkdidact for sharing the link and @kellyoshea for the inspiration. I've never seen this in maths before but it may be that many of you already do it, if so then I'd like to hear your feedback.

The Mistake Game
Students, in pairs or small groups, are given a problem to solve and explain to the class. In their explanation, they must include a deliberate mistake. Not just a numerical slip, but something that highlights a possible misconception that their classmates might have.

If I use this for GCSE revision then past exam questions (the longer, unstructured types) would work best - there's some examples in this excellent set of questions from Suffolk Maths. But this idea could also work when teaching specific topics. I think I may try it this year when teaching both trigonometry and probability trees.

For example, if you use the Mistake Game when teaching Pythagoras' Theorem, you could use this question (solve for x):

The common mistake here is to not square the 4 (though students may come up with something else).

Here's another example, from this worksheet from thechalkface.net.

There's numerous things they could (deliberately) do wrong in this one!

When each group goes through their question on the board, their classmates will be listening carefully to spot the mistake, so it's great for getting students to focus. I'm not sure how best to organise the responses. Perhaps students could put their hand up as soon as they spot the mistake so it can be corrected immediately and then the rest of the solution can be done correctly. Or perhaps when the group have finished presenting their full explanation, a volunteer could come up to the board and correct their work. Or maybe after each presentation the students could discuss the problem in their groups, decide what was wrong and re-do the question correctly.

This is a bit like 'tick or trash' exercises - it's helpful for pupils to be aware of common mistakes. I've also used these 'Classic Mistakes' in previous revision lessons.

The Mistake Game is also a good opportunity for students to see each other’s approaches to solving problems and discuss the effectiveness of different methods.

I think this activity will engage the whole class - I'll try it out and let you know! If you've ever tried anything like this then please share your thoughts. I recommend reading about the experience of the teacher who wrote the original post. As she says, ‘we all learn more when a wrong answer goes up than when we’re simply watching perfection’.

Image: bigthink.com


  1. Great stuff, really interesting idea which I plan to build in. I think it could be particularly useful at post 16 level, I can already see the proof by induction version in my minds eye!

    Do you use deliberate mistakes when working on the board? I find that works well too.

    1. Um, I often use non-deliberate mistakes when working on the board! But that's because I make silly mistakes (it's hard to speak and write simultaneously!), not because of misconceptions! :) It's always nice when students point out a mistake, so you know they're paying attention.

      I like the idea of using this at A level and agree that proof by induction questions are well suited to this type of activity.

  2. Readers of this post might also be interested in this article "My Favorite Liar" which details what may be the best idea ever! http://www.overcomingbias.com/2008/02/my-favorite-lia.html. Thanks to @icecolbeveridge for sharing it.