The missing slice

About this video

When Mum comes home, the chocolate cake has a slice missing. A trail of crumbs runs across the floor to Kian's door, and Kian has chocolate on his chin. Nobody saw anyone take the slice. Does Mum know who ate it? She didn't see it and nobody told her, but she isn't guessing either. Each clue makes the claim "Kian ate the cake" more likely to be true, and anything that does that is called evidence for the claim.

Evidence can point the other way too. If Mum then finds Kian's football boots by the front door, still wet with mud, and a friend's mum writes that Kian has been at theirs all afternoon, that is evidence against the claim: it makes it less likely. A good look at the evidence always asks about both sides.

Evidence is not proof. Even all the clues for Kian don't make it certain: his sister could have left the crumbs, and the chocolate could be from a biscuit. Evidence makes a claim more or less likely, which is why the next question is always how strong it is. It is how we know about things we didn't see happen: detectives find out who did something, doctors what makes a person ill, scientists what lived long ago, from bones. This video goes with the What Counts as Evidence? lesson of Knowledge Level 1 on Knaph.

Transcript

1. 0:00A slice of cake is missing. Nobody saw who took it. Does Mum know?
2. 0:05Crumbs to Kian's door. Chocolate on his chin. Each clue makes it more likely.
3. 0:11But not certain. Maybe his sister left the crumbs. Maybe it's from a biscuit.
4. 0:17Then muddy boots, still wet. And a message, he's been at a friend's all afternoon.
5. 0:23Evidence is how detectives, doctors and scientists know what nobody saw.
6. 0:29Evidence makes a claim more likely, or less likely. Not certain.