About this blog

Physics can be difficult to learn, but this blog aims to help you get into physics by connecting your GCSE physics lessons with things you see in the world around you.

Wednesday, 31 August 2011

5 is the Magic Number

Eagle-eyed readers may have noticed that I’ve been on holiday but now I’m back! It hasn’t escaped my notice that schools go back this week too and I very much hope that a few of you might have slightly better feelings about Double Physics than you may have had before.

I suppose I could commission one of those surveys that the cosmetic people do, asking a handful of people a question like “Do you feel slightly more interested in Physics now than you used to?” and perhaps the result would be that 3 out of 5 people said yes. Hurrah! But if we’ve only asked 5 people, or 10, then you can’t really say that the results are representative of people’s opinions on the whole, can you? These might be 10 of the most fickle people on earth, happy to change their minds at the drop of a hat!

It can be all too easy sometimes when we’re doing Physics experiments to see a couple of results and then decide to jump to conclusions from there without properly checking. And it seems to me this is what those pesky adverts do all the time, which is why I like to keep an eye on the sample size.

But how can you decide that your experiments are showing you a trend? Well, if you were being really diligent then you could just KEEP GOING, with more and more repetitions and getting more and more data. But if you did do that, not only would it be really boring, you may also never have time to do anything else, like draw your conclusions.

So us Physicists use a rule of thumb, that we can draw a trendline (or at least think about it, after all, you have to use your brain here too) once we have five data points. And completing five experiments doesn’t seem like too much of a trial, does it? Conclusions here we come!

Please feel free to contact me if you’d like me to cover any particular topic or expand on things I’ve already covered!

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