Extracting data from Polynomial regression equation

[dunlop407703]

Hi all,

Apologies if this question seams disjointed but I am having trouble organising my thoughts. I've decided just to put what I can into words a hope someone can help.

I have a cumulative data set as follows. I have graphed this data and created a 3rd order polynomial regression equation to allow myself to accurately predict data.

[TABLE="width: 221"]
<colgroup><col><col><col></colgroup><tbody>[TR]
[TD][/TD]
[TD="colspan: 2"]6.35 x 0.15[/TD]
[/TR]
[TR]
[TD]Density[/TD]
[TD]Cum Ash[/TD]
[TD]Cum Yield[/TD]
[/TR]
[TR]
[TD]1.30[/TD]
[TD]3.18[/TD]
[TD]20.32[/TD]
[/TR]
[TR]
[TD]1.35[/TD]
[TD]4.89[/TD]
[TD]32.01[/TD]
[/TR]
[TR]
[TD]1.40[/TD]
[TD]6.21[/TD]
[TD]37.58[/TD]
[/TR]
[TR]
[TD]1.45[/TD]
[TD]7.40[/TD]
[TD]41.48[/TD]
[/TR]
[TR]
[TD]1.50[/TD]
[TD]9.02[/TD]
[TD]45.70[/TD]
[/TR]
[TR]
[TD]1.60[/TD]
[TD]13.62[/TD]
[TD]55.80[/TD]
[/TR]
[TR]
[TD]1.70[/TD]
[TD]16.48[/TD]
[TD]62.29[/TD]
[/TR]
[TR]
[TD]1.80[/TD]
[TD]19.93[/TD]
[TD]69.47[/TD]
[/TR]
[TR]
[TD]2.00[/TD]
[TD]25.36[/TD]
[TD]79.77[/TD]
[/TR]
[TR]
[TD]2.20[/TD]
[TD]38.11[/TD]
[TD]100.00

[/TD]
[/TR]
</tbody>[/TABLE]
From my regression equation I can predict the 'Cum Yield' at an input 'Cum Ash' (x). What I would like to do is be able to calculate the new cumulative results after I remove a fraction from the data. For example if set 'Cum Ash' to 10%, the 'Cum Yield' is returned at 48.22%, based on that outcome I would then like to be able to say "given that I've removed the material up to a 10% cut off, how much of the remaining material do I need to get a sample at 30%".

Any input will be greatly appreciated.

Thanks