Tuesday 17 July 2018

Practical statistics
I think all maths teachers would agree that this is an interesting and important aspect of teaching mathematics. Statistics and the handling of data is one of the most vital applications of mathematics and has implications Read more...

**Practical statistics**

I think all maths teachers would agree that this is an interesting and important aspect of teaching mathematics. Statistics and the handling of data is one of the most vital applications of mathematics and has implications for all aspects of our lives.

Students from a young age need to develop the ‘hands-on’ experience of collecting through practical work in the classroom and surveying opinions. These not only make a welcome change from ‘normal’ classroom activities but bring the subject to life in a way that is difficult to do without this sort of work.

Of course, we now have access to technology which can do large scale statistical simulations as well as large data sets, which enable more thorough analysis to take place – I will look at this in future posts. But it is still worthwhile allowing the students to ‘get their hands dirty’ with actual experiments and data collection.

Before the students have any formal idea of what hypothesis testing is, they can be exploring the sort of hypotheses that will be able to be investigated more thoroughly once they have more experience, maturity and knowledge. Some examples that are very easily done in the classroom include:

**Getting probabilities by relative frequency.**A popular and easy one is the probability of a drawing pin landing point up. If you are confident the drawing pins are all much the same you can pool your results. But this reinforces the difference between theoretical and experimental probability. And there are many variations on this.**Blind tasting – e.g. comparing a ‘value brand’ biscuit with a more expensive version.**This activity can be introduced for younger students, although it can be revisited as they develop their knowledge and understanding (culminating in the formulating and testing of hypotheses at KS5). Even without any formal understanding of significance, students are usually surprised (depending on the choice, of course) by the lack of ability to distinguish between brands. This gives a chance to look at the importance of experimental design, making sure it is blind and random.**The most likely number of throws of a die before a six is obtained.**Definitely pool the results here. And this gives what will be a surprising result for younger students.**Measuring reaction times by dropping a ruler.**You can use this to test the hypothesis that girls have faster reactions than boys.**Surveys.**Best to choose ones where the data can be easily collected, fairly easily classified and preferably on a reasonably large scale, although some discussion of the issues here helps to illustrate the difficulties surrounding reliable statistical conclusions. Examples include the number of children in families and normal method of travel to school.

Gradually introducing students to the placebo effect, the idea of a control group and how double blind trials are important in many trials will help to develop statistical understanding.

**Teachit resources. **

Here at Teachit we have many resources which are useful with practical statistics work. Examples of these include Does the theory match the experiment?, Thread it through - probability, Dice theory and Investigating patterns of random events.

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Tuesday 15 May 2018

A million, a billion, a trillion … who cares?
I have a sneaky feeling that, for a significant proportion of the population, a big number is anything that ends in ‘illion’ and they do not appreciate the differences between them. This was nicely encapsulated Read more...

**A million, a billion, a trillion … who cares?**

I have a sneaky feeling that, for a significant proportion of the population, a big number is anything that ends in ‘illion’ and they do not appreciate the differences between them. This was nicely encapsulated in John Allen Paulos’s book *Innumeracy* where he quotes an American politician who said: ‘A million dollars, a billion, a trillion, whatever. It doesn’t matter as long as we do something about the problem’. A little thought about this reveals its absurdity. A million dollars would not buy a small apartment in New York so it’s unlikely to solve any significant problem in the US. Meanwhile, the entire GDP of the US is less than 20 trillion dollars so spending a trillion dollars to solve a problem is not really feasible without an economic catastrophe.

In the news, we regularly come across references to millions, billions and even trillions. But how many people truly have an intuitive feeling for what these numbers mean? This is an area where, as mathematics teachers, we can dip a toe in the water of politics and morality because, whatever your opinion on these matters, the necessity of basing your opinion on an objective appreciation of the facts is something we can contribute to the debate.

Several years ago, a friend of mine was teaching a mathematics class when he stopped and did a countdown before announcing: ‘I have now been alive for a billion seconds.’ The students were surprised to realise just how long a billion seconds is – almost 32 years. A million seconds meanwhile is merely between 11 and 12 days. A trillion seconds ago, the oldest known cave paintings were being painted by our ancestors. Depressingly, I am not that far off the 2 billion seconds mark now!

As teachers, I think we can contribute to this in various ways. From the very start, students should be encouraged to say numbers properly, eg 3058 is ‘three thousand and fifty eight’ not ‘three oh five eight’, so they begin to appreciate the importance of place value. They should also realise that adding an extra digit has a much bigger consequence than might at first be realised. There are 9 times as many n-digit numbers as there are **all** the numbers with less than n-digits. This is easy to demonstrate by looking at what happens when you move from 2 to 3 digits or 3 to 4 digits.

There is a great website Is that a big number? that deals with these issues in an interesting and engaging way and has examples for students of all ages. For example this link looks at the dimensions of St Paul’s Cathedral. The good news is that students from a young age find big numbers interesting and even funny. So bring them into the classroom whenever appropriate and we may well help to produce citizens who can critically analyse some of the statements we hear daily and that tend to go unchallenged.

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