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

[Peter G.]

Hi,

The question is the following:

Another student proposes that c is proportional to d^0.5 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!

 

[sankalpmittal]

Hi,

The question is the following:

Another student proposes that c is proportional to d^0.5 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 d^1/2 ? 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.

 

[Peter G.]

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

 

[Redbelly98]

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.