You are Here: Home

# Stats homework help

1. haven't done stats in ages so need some help here

Classes of students, from three different schools, sat the same examination paper. The mean scores for each school were 63, 38 and 72 %. If the respective class sizes were 23, 30 and 15, find the mean mark of the schools taken together.

How do I do this?
2. (Original post by not_lucas1)
haven't done stats in ages so need some help here

Classes of students, from three different schools, sat the same examination paper. The mean scores for each school were 63, 38 and 72 %. If the respective class sizes were 23, 30 and 15, find the mean mark of the schools taken together.

How do I do this?
Think about it this way, if there were 30 pupils each from school A and B, and if the average marks were 60 and 80, then the average between the two schools would be 70. This is because they're equal so it almost seems like you're not taking a weighted average.

Whereas if there were 15 in a class that got an average of 85, and a class of 45 that got an average of 65, then the average would be 70 (weighted towards the class with more students). So if you've not come across it before, it's worth looking up what a 'weighted average' is.

The other way to think about it is to deconstruct and reconstruct the mean. Eg if there were 15 that got 85 then the total score is 15*85 there, the other class has a total score of 45*65.. so the new total score is ...and the new total population is.. and so the new average is...

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: September 25, 2016
TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Today on TSR

### Is this true about Oxbridge?

Should I still go?

### What stereotype are you breaking?

Poll
Useful resources
Study resources

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.