Saturday, 31 May 2014

A Lesson: The Capture-Recapture method

I am teaching GCSE Statistics for the first time ever this year. I am lucky to be working with an able group of Year 10 students - all 24 achieved a level 8 on their end of Year 9 assessment - and I expect them to do well in their exam this summer.

I began the year with grand ideas about creating lots of engaging lessons. For example, in one of our first lessons in September, we used Spearman's Rank Correlation Coefficient to test the correlation between the scores given by Strictly Come Dancing judges. We then gave 8 vegetables a score out of 10 and used SRCC to find our perfect vegetable partner within the class!


However, I have not designed and taught as many lessons like this as I had hoped, largely due to the significant time demands of the Controlled Assessment part of the GCSE.

Just before the May half-term holiday I decided it was high time we had a more engaging lesson and I planned the following lesson on the Capture-Recapture method. This was largely inspired by Julie Reulbach's blog about a lesson on the same topic.

I began with this video which is a great introduction to the topic and then explained that students were going to work in pairs to conduct their own capture-recapture experiment. Each pair of students received a lake with fish in and some tags (or a bowl of Weetos plus some Froot Loops on the side!)


Students had the support of the worksheet below but the rest was left up to them.


I was particularly keen to avoid teaching students a particular method for calculating their estimate of the total population. The text book gives the formulas below but as far as I am concerned this topic is just some reasonably straightforward proportion work and the formulas make for unnecessary complications.


Students seemed to enjoy the lesson, certainly understood the method and, most importantly of all, I had plenty of spare Froot Loops to take home for my 3 year old daughter!

About to start
'Fish' now 'tagged'


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