Three median line.

[Studyinghard]

Not sure if this is the same but go into scatterplot - analyse - regression - median to median.
is that the three median line?

[_avO]

Yes it is, luckily I found out before tomorrow

Also it's Stats->Calc-MedMed Line for ClassPad for anyone who didn't know

Also if you want to manually find the y intercept (as you can find the gradient by observation) use the rule

c = 1/3[(yl + ym + yu) - m(xl + xm + xu)]

[superstar1]

yeh u would have to for 2 mark questions regarding 3 median line.

[Studyinghard]

Yes it is, luckily I found out before tomorrow

Also it's Stats->Calc-MedMed Line for ClassPad for anyone who didn't know

Also if you want to manually find the y intercept (as you can find the gradient by observation) use the rule

c = 1/3[(yl + ym + yu) - m(xl + xm + xu)]

yay! I always struggle with three median line and now i can just chuck it in the CAS
Also i knew about this, from a practice exam yeah? cant rememebr which one =/

[superstar1]

yeh it was from insight i think...

[LFTM]

Yes it is, luckily I found out before tomorrow

Also it's Stats->Calc-MedMed Line for ClassPad for anyone who didn't know

Also if you want to manually find the y intercept (as you can find the gradient by observation) use the rule

c = 1/3[(yl + ym + yu) - m(xl + xm + xu)]

How come i've never seen this rule? Where do i get all those values from?

[_avO]

when you separate the graph into 3 sections, yl represents the lower median y value, ym represents the middle median y value, xu represents the upper median x value and so on

[Xavier1234]

Yes it is, luckily I found out before tomorrow

Also it's Stats->Calc-MedMed Line for ClassPad for anyone who didn't know

Also if you want to manually find the y intercept (as you can find the gradient by observation) use the rule

c = 1/3[(yl + ym + yu) - m(xl + xm + xu)]

How come i've never seen this rule? Where do i get all those values from?

from the three groups that you do on the scatterplot, Yu = y-value Upper group, YL=y-value lower, Ym=y-value middle, and so on..

[LFTM]

when you separate the graph into 3 sections, yl represents the lower median y value, ym represents the middle median y value, xu represents the upper median x value and so on

Oh but this is without calc?
And thanks for letting us know, i never knew you could do the 3 median line on calc. My teacher never said anything about it.

[Blakhitman]

If you have the gradient and at least one point on the line, why can't you just use y=mx+c to find the y-int?

[Streaker]

Wait so just to confirm, the median-median function on my CAS is essentially the same as doing it manually (i.e. splitting the graph up into three sections and finding medians then plotting etc)

[_avO]

If you have the gradient and at least one point on the line, why can't you just use y=mx+c to find the y-int?

because it gets shifted up or down 1/3 depending on where the middle median X,Y values are, so its not always accurate to do this method

Wait so just to confirm, the median-median function on my CAS is essentially the same as doing it manually (i.e. splitting the graph up into three sections and finding medians then plotting etc)

No it also automatically shifts the line 1/3 (as mentioned before) and makes an accurate calculation of the y-intercept

An alternate method is to find all 3 median coordinates, find the gradient and then use the formula I wrote a few posts ago

[Blakhitman]

Wait so just to confirm, the median-median function on my CAS is essentially the same as doing it manually (i.e. splitting the graph up into three sections and finding medians then plotting etc)

If they ask you to plot it, then do it by hand cause they wanna see if you know how to sketch a three-median line (simply drawing what you see on CAS, isn't right I don't think). Also they ask you to circle the points you used so there's no escaping splitting the graph, and if you've split it, then that's the hard bit done.

[Blakhitman]

If you have the gradient and at least one point on the line, why can't you just use y=mx+c to find the y-int?

because it gets shifted up or down 1/3 depending on where the middle median X,Y values are, so its not always accurate to do this method

Wait so just to confirm, the median-median function on my CAS is essentially the same as doing it manually (i.e. splitting the graph up into three sections and finding medians then plotting etc)

No it also automatically shifts the line 1/3 (as mentioned before) and makes an accurate calculation of the y-intercept

An alternate method is to find all 3 median coordinates, find the gradient and then use the formula I wrote a few posts ago

lol I keep forgetting that.

While we're at it, why is that necessary? Also how do they judge what 1/3 is?

[Studyinghard]

Now that I think about it more this is really important to perfect answers! its okay, you all can thank me later when theres a draw a three median line question in the exam and you just sit there chilling plugging into your calc. while others do the retarded way muhauha