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ecoli

Inverse or Indirect?

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I have gotten several different and conflicting definitions from teachers over the past few years.

 

One teacher described a graph with a decreasing y-axis value and increasing x-axis value as an indirect relationship, wihle another teacher calls this inverse relationship.

 

graph.bmp

 

What's the difference, what the correct relationship, what do the graphs look like?

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When we say two variables are inversely related, we usually mean something along the lines of:

 

[math]x \propto \frac{1}{y}[/math]

 

What you've drawn there is clearly linear; I don't think that either of the two words really describe it. I've never really heard of something being an indirect relationship either.

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I would have said either that x is inversely proportional to y.

 

[edit] but "x is indirectly proportional to y" doesn't sound too wrong either.

 

[edit2] thiking about it I'm not really that sure, I may have said "indirectly proportional"... it's almost the same thing anyway.

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The phrase "x is inversely proportional to y" has always conjured the expression that I gave above (at least to me). This would imply the graph looks something like y = 1/x, but clearly it doesn't.

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As I was always taught, indirect relationships are any function in which all x's decreases as y increases. A direct relationship would be one in which all x's increase as y increases. We don't use the term as much in school for calc as we do for economics.

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That's what I was told by by econ teacher. But my physics teacher tells me differently.

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that graph is x proportional to -y, I've never heard it described as inversly or indirectly related though, as Dave said inverse is normally y=k/x where k is some variable...

 

I would be inclined to belive the physics guy, but I'm biased...

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Well, for one thing k would be a constant, not variable. But I think you hit upon what I've been trying to say.

 

Inverse relationship means it's proportional and I would assume implies that it's actualy a function that we are questioning.

 

Indirect just means that one goes down as the other goes up. There doesn't have to be any proportionality in it.

 

Does that make more sense ecoli?

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So inverse would be a more general term, right. Yeah, that makes perfect sense, thank you.

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The issue of direct versus indirect is an issue of whether there is an intermediate step or process involved.  If there is no intermediate step, there is a direct effect.  I there is an indirect effect; A effects B which in turn effects C.

The issue of direct versus inverse is an issue of whether two variables move in the same direction or against each other.  If A rises when B rises, there is a direct or positive relationship.  If A falls when B rises, the is an inverse or negative relationship.

It reminds me of right versus left and right versus wrong.  Right versus left deals with direction and right versus wrong deals with morality.

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