S1 Interpolation Formula

I've been looking everywhere for this. My teacher taught me an easy formula for working this out (quicker than drawing out diagrams.) But I'm resitting and can't consult that teacher, so I'm stuck onto what it was.

I know it's something like: lower boundary + (something?)/frequency) x class width.

Any help?

Reply 1

Zacken

22

Original post by Save.Me

I've been looking everywhere for this. My teacher taught me an easy formula for working this out (quicker than drawing out diagrams.) But I'm resitting and can't consult that teacher, so I'm stuck onto what it was.

I know it's something like: lower boundary + (something?)/frequency) x class width.

Any help?

It comes straight from the diagram though. Draw the diagram out and re-arrange for the value you want and that'll give you your formula.

Reply 2

Save.Me

OP

13

Original post by Zacken

It comes straight from the diagram though. Draw the diagram out and re-arrange for the value you want and that'll give you your formula.

There's an easier and quicker way than that. I learned it in college. I don't understand the diagram at all.

Reply 3

Zacken

22

Original post by Save.Me

There's an easier and quicker way than that. I learned it in college. I don't understand the diagram at all.

Are you talking about

Median = Lower bound of class + [class width/frequency] * n/2 or rank?

n/2 is your total frequency divided by 2 to get the median, it's also often called the rank.