to think this was an unfair way to select children

[3boys40]

Given a number between 2 and 12 starting at the front of class. Than rolling a dice to select said children. You would think a maths teacher should know that gives certain children an unfair advantange. My poor ds who sits at the the front had no chance with 2.

X crossed... Sorry OP, that's a bit annoying/unfair to your DS, YANBU

aw. that's a shame. Maths teacher should understand probability and not use unfair methods to pick children.

Was it choosing them for something, or a way of illustrating probability?

Oh, cross post. Maybe something to bring up at said parent's evening!

x-post. Still maybe he didn't realise anyone would be so keen to do it.

That is a bit rubbish then!

Perhaps number 7 thinks it's unfair too if they hate parents evening!

After my maths lesson just now, yes that is unfair OP.

It doesn't make any difference to the probability whether the dice are rolled at the same time or one after the other, 2 is still less likely than 7.

Say you want to get a 2, and you are rolling one after another. On the first roll, you must get a 1. Probability 1 in 6. On the next roll you must also get a 1. Probability 1 in 6 again. Probability of a 1, then a 1 again is 1/36

Compare that with trying to roll a 7. On the first go, you need to get a 1 or 2 or 3 or 4 or 5 or 6, it doesn't matter, any of them could combine with a second roll to add up to 7. Probability 6/6 - it's definitely going to happen.
Once you have rolled, then you need to get whichever number on your second roll that adds up to 7. Probability 1/6. Overall probability 1/6.

Two dice? Aha!

was not being used to teach maths though. (cross post)

sorry i was way behind there. just connected to wifi

What would a fair way to choose be?

Completely randomly?

Or the most sensible students/best at maths/ones the teacher likes best?

These things aren't always fair.

I'm pondering LOBAHW 's percents.

Do yiu need to count 4and2 as well as 2and4, etc? [puzzled]

Shes still right though as friffing allus the middly numbers have a higher chance if being thrown.

Poor show from the teacher. Ugh.

names in a hat of those children wanting to help would be good.

Does it really matter though? Kids don't get picked for everything, I'd sympathise with the child and then move on.

it was ds who pointed out the unfairness of it. I just said never mind at least you can go to cubs but I could tell he was upset. Was also recently not picked for a more able programme despite being on a higher level than a child who was. I guess I am also disappointed as he had just left a school where many of the parents worked at the school and their dc appearred to get an unfair proportion of the best school play parts, etc etc

Chaos - you have to count "4 and then 2" as well as "2 and then 4". If you want to see all the results, you can draw out a square 6 by 6, put 1-6 along the top (outside) for the first die and then 1-6 down the left for the second die and add up the total in each square. Then get highlighter pens for each total.

Pull straws?

Right. So. There are ten kids in the class(?)

In order to select a helper for parents' evening, the teacher gave each of them a number between 2 and 12, and rolled a pair of 6-sided dice to pick a number.

Is that what happened?

(The dice probability is a normal distribution, isn't it?)

It gives them more chance than if the teacher just selects the ones he wants (and they are not one of them)
I actually think given it was a maths teacher, he was waiting for someone to pipe up and point out the unfairness! Teaching and learning doesn't have to just happen in lessons!

odds just seem unfair for 2 or 12 for that mattdr but its done now.

thats the thing. He is too shy to do that.