Date: Nov 27, 2012 3:22 PM
Author: Ray Koopman
Subject: Re: OK – I think I’m set, at least till we get t<br> o c on (e, u, u*e).
On Nov 27, 6:19 am, djh <halitsk...@att.net> wrote:

> 1.

>

> You wrote:

>

> ?slope = dy/dx = a1 + 2*a2*x?

>

> Oh! That slope! (Of the tangent to the quadratic at x = 0.) Duh!

>

> I was construing ?slope? as just a alternative term for ?coefficient?

> ? don?t know why. Someday I?ll learn if that if I can?t make sense

> of something you?ve written, then I?ve construed something wrongly.

>

> 2.

>

> When I re-run the analysis, I will use (u/1+u) instead of u. So I

> assume I would use ln(u/(1+u)), and (ln(u+(1/u)))^2, parallel to

> ln(u) and (ln(u))^2? (Unless you don?t want me to take logs ? please

> clarify here.)

I intended no logs. Also, I worry when I see u/1+u and u+(1/u),

neither of which equals u/(1+u).

>

> 3. You wrote:

>

> ?For instance, you might get the slope at each data point and then

> use their literal average, a1 + 2*a2*mean_x. But what if cells with

> different x-means give the same a1 and a2? Should their "average

> slope" measures be the same or different? That's the kind of question

> you have to ask yourself.?

>

> Since I can?t think that far ahead in the abstract (as you can), I

> will use ?a1 + 2*a2*mean_x? initially, and see if any peculiarities

> arise of the sort you mention (or others.)

Here's a f'rinstance. First, remember that a quadratic can always be

written as A + B*(x - C)^2. Next, suppose that two cells have the

same A,B,C, but mean_x is < C in one cell and > C in the other, so

that their average slopes differ. Then, if the difference in mean_x

is an intrinsic property of the cells then the average slope is

appropriate, but if the difference in mean_x is arbitrary, a result

of experimenter whim, then the average slope is not appropriate.

>

> 4.

>

> [...]

I'll respond to 4 later.