Home > cross-curricular, Maths, Pedagogy, Teaching > Probability and Sex Ed

## Probability and Sex Ed

This week we had our third CT day of the year. (CT Days, or citizenship themed days, are collapsed timetable days where pupils do a range of topics linked to a theme.) I was with my coaching group and we had a great day on the topic of “personal wellbeing”.

The new year 11 (we move up year groups at spring bank) had a day on sexual education. Currently in maths they are learning about probability and one of my colleagues and I decided this was a perfect opportunity to merge the two.

We gathered some data on the probabilities if contracting STIs from an unprotected sexual encounter and they looked at the probabilities involved in contracting things after multiple encounters (here).

We also looked at expected values, and given the effectiveness of different types of contraception, (from here) how many pregnancies a year would you expect if a couple who were always safe made love twice a week. The answer shocked the whole class. They were also amazed by the difference when I asked them to complete tree diagrams and work out the expected value if the couple used condoms and the pill.

This was a much easier concept for them to relate to than picking sweets out of a bag as they could see that this was something that would affect everyone at some point in their lives. It also got across some messages that are important, especially as our school is located in an area with quite a lot if young parents.

1. June 29, 2013 at 11:05 am

That is brilliant.
Absolutely fantastic real life Maths.

Where did you find the data/probabilities from?

Dave

• June 29, 2013 at 11:36 am

I’ve added a link to contraception data I found and used (and tweeted you it), not sure where STI data came from as it was my colleague who found it, but I will find out on Monday and add a link.

2. June 30, 2013 at 2:07 am

I love the idea! But aren’t the contraception effectiveness rates already annual effectiveness rates, not per-use rates?

• June 30, 2013 at 7:45 am

I thought they were per use, but having reread the site it is unclear. Either way, I think it still valid to use for the purpose of the lesson.

• June 30, 2013 at 7:47 am

Talking about per year rates, you could then open the discussion to, “of the x girls in year 11…”