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How to find midpoints?

Hi,

Can you guys help me with the following question? I'm unsure as to how to find the midpoints in order to find the mean. I have found midpoints in other questions but this one seems to be different as I can't seem to get the answer right (the first midpoint should be 45, I don't know how). Here's the question:

I'd really appreciate all help!

Thanks in advance,

Methew

Reply 1

username456717

Original post by methewthomson

I'd really appreciate all help!

Thanks in advance,

Methew

The image link doesn't work.

Reply 2

methewthomson

Original post by nebelbon

The image link doesn't work.

Sorry about that. I'm pasting it again:

Thanks

question 6.png40.3KB

Reply 3

Doctor_Einstein

Original post by methewthomson

Sorry about that. I'm pasting it again:

Thanks

The first midpoint is actually 20, but since the frequency for this category is 0 you can ignore it.

The next midpoint (the first point of any significance) is midway between 40 and 50, that is 45. This is why they mention it as the first midpoint.

The next midpoint is 55, then 62.5 etc.