Math Is Fun Forum

Alive

Member

Registered: 2010-08-14

Posts: 92

q correlation coefficient (diagrams from textbook provided)

The thing I don't understand is how does finding out the median help you drawing in the horizontal and vertical lines. How do you know if it's going to pass through a few of the data points? Like in the example on that website it has a moderate negative correlation and the median is the 8'th score. How did they put the vertical+horizontal line by knowing the median? I see 6 data points in the B quadrant, 5 in the D quadrant, 1 in both A and C. How did they know all this by just the 8'th score? Thanks.

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All things can be forgiven if we can progress.
Yusuf Islam (formerly known as Cat Stevens)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: q correlation coefficient (diagrams from textbook provided)

Hi Alive;

Doesn't step 2 and 3 explain what you have to do?
Looks like a very good text book what is the title?
Where are the data points?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Alive

Member

Registered: 2010-08-14

Posts: 92

Re: q correlation coefficient (diagrams from textbook provided)

The textbook is 'Maths Quest 11 Standard General Mathematics TI-NSPIRE EDITION'

So there are 15 pieces of data (I'm guessing that is the data points?) you find the median which is the 8'th score which is lovely but how on earth do you know where to exactly put the vertical and horizontal lines? It has different examples and all of them are different. Sometimes it goes on them points sometimes it doesn't. I don't get how it is done...

---

All things can be forgiven if we can progress.
Yusuf Islam (formerly known as Cat Stevens)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: q correlation coefficient (diagrams from textbook provided)

Hi Alive;

You haven't provided the 1st set of data points so we will have to use the 2nd example.

See the row called hours spent training? Call that x and then sort it.

{2,3,4,5,6,7,8,9,10,10,12,13,14,16,18}

The median is the value in the middle in this case 9.

Find 9 on the x axis and draw a vertical line.

See the row called Number of errors during the first week?

Call that y and sort it.

{6,6,8,8,15,16,18,22,24,24,25,27,31,34,43}

The median of the y's is in the middle in this case 22.

Find 22 on the y axis. Draw a horizontal line there.

That is it.

Can you now do problem #1?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.