Prove it! What is proof?. Sureness Certainty How sure can we be?

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 right

His 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