Prove it!

What is proof?

Sureness•Certainty•How sure can we be?

Kinds of proof • Mathematical• Scientific

Mathematical proof

• Prove that 7x3=21• 3+3+3+3+3+3+3=21• Proofs mean that you can make rules, so 7x3 is always 21

Pythagorus theorum

• the square of the hypotenuse=squares of other 2 sides

Pythagorus was rightHis logic was worked out step by step. It is completely correct because every

step leads on from the last.

Scientific proof is different.

The Chocolate Conjecture

• Eating chocolate before you do sums will make you brainer. You will be able to get more sums right!

• PROVE IT.

Design a good tests to investigate the chocolate conjecture

• This is scientific proof. • We need to do a test to find

out. • What would you do? • How would you do it?

Sums sheet

• 1+3 =• 2+1 =• 1+1=• 3+2=• 2+2=

Good tests

• Comparisons• Equal comparisons – control

groups• Before and after• Useful measurements• Logical reasons for changes• Placebo effects

why do we need fair tests?

• what happens when we don’t do good tests?

• what could go wrong?

Why do we need fair tests?

how did we find out?

• science is about noticing things and thinking about WHY

• scientists can test ideas and find out if they are right or not

• this saves lives!

people used to think smoking was good for you

how did we find out that smoking harms us?

• science!

doctors who smoked

doctors who didn’t smoke

50 years passed

scientists compared the two groups people who smoked had more diseases and died younger

this showed smoking harmed us

• lots of other studies in different places showed that smoking harmed us too

• we are very sure that smoking is bad for us

scary statistics

• do you ever see scary statistics?• would you like to help your mum and dad

when they read newspapers?

Broomhill School Science Week 2013

ONLY £500!

STOP ZOMBIES! NOW !

cut risk of ATTACK by zombies by 50% !!!

BROOMHILL NEWS – science week 2013

• £500 to cut the risk of zombie attack by 50%

• that’s cutting the risk of attack in half!• would you buy it?

but...

• cutting the risk in half with a zombie kit sounds good

• but what was the risk to start with? • what’s it half of?

• 100% RISK OF ZOMBIE ATTACK

• Means the Kit can cut the risk to 50%

But

• 1% risk of Zombie Attack• HALF OF 1% means the kit reduces the

risk of attack to 0.5%• DOESN’T SOUND AS GOOD!

• BUT zombies DON’T EXIST

• there is NO CHANCE OF A ZOMBIE ATTACK

• The Zombie Kit cuts the risk by 50%• BUT HALF OF NOTHING IS NOTHING• SO THE KIT IS RUBBISH

STOP 90% OF ALL PAPERCUTS!

GREAT NEW INVENTION!ONLY £100!

BUT!

• ONLY 10 out of 1000 of children get a papercut every year

• if we cut the risk of papercuts by 90%• instead of 10 out of 1000 children with

papercuts• it’s 1 in 1000• but you have to wear gloves all the time!

things that sound good might not be

• Science is about looking, thinking and testing

• when we don’t do fair tests, we make mistakes and harm people

• sometimes numbers can trick us - so we have to be careful