Why Might Plotting log c Against log d Not Be the Best Test for Proportionality?

AI Thread Summary
The discussion centers on the proposal that variable c is proportional to d raised to the power of 0.5. A suggested graph is log c = 0.5 log d, while the mark scheme accepts log c = log d. Participants debate the validity of these equations, questioning whether c is directly proportional to d^0.5 and highlighting the importance of constants in proportionality. Some express confusion over how the mark scheme's answer aligns with the original proposal. The consensus suggests that the mark scheme may have overlooked the necessary 0.5 factor in the relationship.
Peter G.
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Hi,

The question is the following:

Another student proposes that c is proportional to d0.5 State a suitable graph that can be plotted to test this proposal.

I suggested plotting log c = 0.5 log d.

One of the answers the markscheme accepts is log c = log d

Can anyone tell me why my answer is wrong?

Thanks!
 
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Peter G. said:
Hi,

The question is the following:

Another student proposes that c is proportional to d0.5 State a suitable graph that can be plotted to test this proposal.

Inversely proportional or directly proportional ?

I suggested plotting log c = 0.5 log d.

One of the answers the mark scheme accepts is log c = log d

Can anyone tell me why my answer is wrong?

Thanks!

Is c directly proportional to d1/2 ? If so , then equation cannot be log c = 0.5 log d.

Anyways what's precisely is question asking for ? Your answer seems to be wrong because you missed the constants involved in proportionality.
 
It is supposed to be directly proportional I guess, since they want a straight line through the origin.

I just don't understand how you can get lg c = lg d like the mark scheme asks for
 
Peter G. said:
I just don't understand how you can get lg c = lg d like the mark scheme asks for
The mark scheme appears to be wrong. Perhaps the person who wrote it accidentally left out the 0.5 factor.
 

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