## Mathspigs Unite!!!

March 31, 2009

I am not alone. There are other mathspigs out there trying to inform the public about rubbish maths.

Chris Berg commented in The Sunday Age 21st December, 2008 that the Federal Government Preventative Health Taskforce claimed that obesity cost Australia  \$58.2 billion a year.

“We are used to reading enormous numbers like that every day in the press. But for the most part, they consist of so many assumptions piled upon yet more assumptions that they are worthless.’ commented Berg.

How do you work out how much obesity costs??? Um, you guess. Pick a number, double it, that sort of thing.

There is a direct cost to the community for medical treatment of obese patients. This according to the Taskforce’s report was \$8.3 Billion in 2008.   That hardly adds up to \$58.2 billion. But wait according to the report:

’This includes an estimate of \$49.9 billion for the impact of obesity on quality of life.’

#mce_temp_url#

http://www.preventativehealth.org.au

So the Taskforce is guessing Oh, um, obesity costs about \$49.9 Billion in lifestyle costs. What is it? I’ll tell you. One hell of a lot of fairy floss.

## Graphs for the Lost and Bewildered

March 31, 2009

Many, many tables and graphs have been published leading up to and during the current global financial crisis. The GFC, as it is called. But mathspig wants students of all ages to know that they can be mislead, ripped off and/or lose their life savings if they cannot read graphs properly.Mathspig found the following graphs in full page ads in Good Weekend The Age 26th July 2008, Sunday LIfe The Sunday Age 3rd August 2008 and The Weekend Australian Magazine, The Australian 2-3rd August 2008.

Mathspig is not saying that AMP set out to mislead investors but it would be easy for anyone unfamiliar with graphs to jump to the wrong conclusion. Why?  Have a look at the graph.

What’s the problem???? Have a look at the scale on the vertical or y-axis. it is not linear. In fact, it is logarithmic. It keeps doubling as you move up the y-axis. This  compresses the graph dramatically at the top. The following graph is clearer. It is a linear graph representing another ASX Index this time  the TOP 200, but it gives a much clearer picture of the the movement of share prices on the stockmarket in the US Sub-prime/oil crisis marked on the graph above. In fact, share prices dropped by nearly 50% from November 2007 to August 2008.

## And the Wheel on the Roulette table went round and round, round and round…

March 31, 2009

Gamblers believe in stuff. They believe in lucky numbers, lucky breaks, lucky colours and even a lucky rabbit’s foot (It wasn’t so lucky for the rabbit.) But more than anything else gamblers believe in patterns.

If we flip a coin an infinite number of times Heads:Tails ratio will be 50:50. But if you think of infinity as a long, long ribbon with a HTTHTHHTTT pattern then random flips means any pattern is possible. 10 H in a row is possible… or 20 H. It’s just that we suddenly see meaning in this pattern.  This is the Gambler’s Fallacy. We see 10 H in a row and we say ‘Aha! The next flip has to be Tails.’  But it doesn’t have to be Tails. The next flip – as with all flips – has a equal 50:50 chance of being Heads or Tails. That’s all. But we are surprised when we see an extended streak of, say, Heads. What has happened in the past does not effect THE NEXT FLIP!!!!!

Roulette Wheel has 36 numbers and an equal number of Red and Black slots. ‘The most famous example of such a phenomenon occurred in a Monte Carlo Casino in the summer of 1913 when a roulette wheel landed on black 26 times in a row.’ The Decisive Moment How the Brain Makes Up Its own Mind   Jonah Lehrer (Text Publishing 2009)

What do you think the gamblers did that night??? After a few Reds in a row they started to think it was Blacks turn and kept backing Black.

The Casino kept raking in the francs that night. It was a very good night for the house.

So mathspigs try it. Each student should flip a coin for, say, 5 minutes and record HHT etc. How long was the longest run of H or T?  You could convert this to a Bar Graph with the no. of Students on the X-axis and Number of H/T in a row on the Y-axis.

## iPod Shuffle: Don’t Play It Again Sam!!!!!!!

March 31, 2009

Here is another example of Gambler’s Fallacy, but for non gamblers.

We see – in this case – hear a pattern and then attribute meaning to this pattern  - It’s a conspiracy!!!! - when there is no pattern and no meaning!!!!! So Apple found when designing their iPod shuffle feature.

“When Apple first introduced the shuffle feature on its iPods, the shuffle was truly random; each song was equally likely to be picked than any other. However, the randomness didn’t appear random, since some songs were occasionally repeated, and customers concluded that the feature contained some secret patterns and preferences. As a result, Apple was forced to revise the algorithm. ‘We made it less random to make it feel more random,’said Steve Jobs, the CEO of Apple’   p68 The Decisive Moment How the Brain Makes Up Its Mind Jonah Lehrer (Text Publishing 2009)

Try it. Pick 12 songs maybe off your playlist  - Your MP3 player, perhaps or a Top 20 Chart or Top 20 Downloads Chart – assign each song a number: 1, 2, 3….up to 12. Take two dice (Diehards Note:  It’s 1 die, 2 dice) and roll. How many throws until you get 2 songs played in a row?

## How many bedrooms in Australia?????

March 30, 2009

According to this article in The Age (26th March, 2009) 37% of homes have 4 bedrooms or more.

In fact, this statistic is a little ambiguous. Did they mean 37% of new homes have 4 or more bedrooms??? Or all homes??

According to the Yearbook Australia 2008:

Dwellings with:

1 bedroom     4.0%

2 bedrooms   19.7%

3 bedrooms 47.8%

4 or more bedrooms  28.3%

As there are 7.9 million private dwellings in Australia today, we can work out the total number of bedrooms. Get going… Send MathsPig the answer.

1301.0 – Year Book Australia, 2008

## Real Men Eat Red Meat and Die!!!!

March 27, 2009

Here we go again.

According to this  headline in THE AUSTRALIAN 25th March 2009   meat eaters are at risk of dying of  cancer. The study published in  Archives of Internal Medicine involved half a million people over 10 years. So far so good. That is a good sample size. The sample consisted of people aged 50 to 71 years at baseline or, obviously, after 10 years 60 to 81years!!!!  So some deaths would be expected. Nevertheless, the article states:

“Men whose red meat intake put them in the top 20 per cent consumption band were 22 per cent more likely to die of cancer in the 10 years of the study, compared to men whose intake was in the lowest 20 per cent. For women, there was a 20 per cent increase in risk.”

Here is the problem. Firstly and I quote from the original study: “Meat intake was estimated from a food frequency questionnaire administered at baseline.’ So they asked people once what their eating habits were then assumed they continued for the next 10 YEARS??? How likely are your eating habits to change in 10 years???

Secondly, and this was mentioned  in the article without explaining the maths, big meat eaters tend also to be big drinkers, smokers, obese and the rest. This study has tried to separate out meat eating from other unhealthy lifestyle choices using the Cox Regression. Mathematical wizardry has produced these numbers but they don’t mean much.

If the study used a control group of drinking, smoking, obese vegans then compaing mortality rates over 10 years would be would be interesting. But where do yo find half a million of them????????

Finally,  the study  concluded ‘Red and processed meat intakes were associated with modest increases in total mortality, cancer mortality, and cardiovascular disease mortality.’ Not the stuff of headlines at all!!!!!!!

March 24, 2009

## Homework: Fun and Entertainment for All the Family by Kerry Cue

March 24, 2009

As a teacher I was often asked by parents ‘How do you get kids to do their homework?’ It’s the \$million question. If anyone has the answer they could sell it on eBay and make a fortune. Short of advising parents to try using a whip, a tranquilliser gun and/or the threat of grounding offspring until they are 45 years old, I have no easy answers. No one does.

I was first asked this question over 25 years ago but I was reminded of the desperation of parents last week. I was addressing parents from several primary and secondary schools when the question cropped up yet again. As soon as the audience heard the desperate query they gave out an audible sigh, a combined plea for help. Most parents realise that homework is worthwhile. It teaches kids self-discipline among other skills. And, just between you and me, most kids know that homework is important too.

It’s just that homework involves self-discipline and self-discipline is hard work. During the holidays a kid gets to sit in front of the tellie with the remote, a bag of chips, a drink in their hand and their feet on the coffee table. It’s the good life. Then term time comes around and it’s ‘Homework. Homework. Homework’. They moan. They protest. They grumble. Of course, they do. If self-discipline was easy the world would be full of thin, fit, rich, non-smoking people who are not addicted to love. As the kids would say, self-discipline sucks!

But I can help parents out here. Just a little. After talking to the parents I then spoke to a combined group of Year 5/6 students the next day about homework. I didn’t nag. I didn’t talk about the importance of homework. I simply read them this story I wrote from real life and – Guess what? – they laughed:

My Homework Diary by Danno Year 7

Tuesday 2nd April

6.00pm Homework. History project.

6.01         Sit at desk. Start.

6.02         Stop. Can’t find pencil.

6.03         Find pencil. Start. Stop. Can’t find paper.

6.05         Find paper. Start. Stop. Pencil blunt. Can’t find sharpener.

6.07         Little brother walks past door. Run out. Punch brother. Brother yells. I yell ‘He’s interrupting my homework’. Mum yells at brother. Ha! Ha! Go back.

6.09         Sit at desk. Look out window. Brother’s up tree. Run out and throw tennis ball. Miss. He spits on me. The pea brain. Climb after him. Intention. Murder. He yells. Mum comes out. ‘What are you doing?’ she asks. ‘My homework’ I say. ‘Up a tree?’ She has a point. ‘I’m taking a break.’ (I sure am. I’m going to break the little twerps leg if I catch him.) ‘How can you take a break? You’ve only been in your room 5 minutes.’ ‘Nine minutes and 45 seconds’ I add. I go back.

6.11         Sit at desk. Damn. There’s a fly. Throw things at fly. Miss. Damn. I’ll get that fly. WHAM. Got him. Fly squashed all over homework book. Uek! I can’t do homework now.

6.18         In kitchen making coffee. ‘What are you doing?’ mum asks. ‘I can’t do my homework’ I explain. ‘There are fly guts squashed all over my homework book.’ Mum wipes book. ‘What about the germs?’ I ask. Mum sprays book with disinfectant. Damn.

6.27         Need music. Put on CD. LOUD. ‘Turn it down.’ ‘What?’ Dad nearly rips handle off door. ‘TURN IT DOWN’. ‘No need to yell.’ I yell. Dad’s face is a stoplight. All red. I turn the volume down to 9.. to 7 ..to 4. Dad’s face resumes normal transmission. He’s pink again.  ‘You can’t study with that racket’ says dad. I give him my tennis racket. Dad snorts and leaves.

6.39         Sit at desk. Work. Work. Great. That’s the best dagger tattoo I’ve drawn on my arm yet. I’ll put in some blood. Ahh! Biro’s leaked everywhere. Wipe off with paper. 10 sheets.

6.47 Brother makes faces through window. Throw book at him. He bolts. Damn. It was my homework book.

6.53 Got book off dog. Read homework sheet. Answer questions on page 47. There’s no page 47. Of ANCIENT CIVILISATIONS. Oh No! I’ve got ANCIENT WARFARE. Cool pictures but. They cut off their heads. Gruesome.

6.58         Write ‘Ancient Ejypt’ on page. Um. Ejipt. Egipd. Yell ‘Mum, how do you spell Egipd?’ E.G.Y.P.T.’ And Ancient?’ (She should know! Ha!) A.N.C.I.E.N.T. Thanks. Write ‘Ancient Egypt’ on page. Good.

7.01 ‘Dinner’. Great. I’m starved. I should be but. I’ve done an hour’s homework.

I only added one more comment. If you want to get your homework done don’t do it like Danno!!!!!

http://www.kerrycue.net                                               Canberra Times 25/3/09

Pic#Author at St Kevin’s Parish School in the 50′s