sushma_roberts
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Hiya can I get some help on this question please!

Attachment 739954

Using data from the first second of forced expiration, calculate the percentage
decrease in the FEV for group B compared with group A.
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QuentinM
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No i can't

(because the attachment is not found apparently-can you reupload?)
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sushma_roberts
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Ah right sorry

(Original post by QuentinM)
No i can't

(because the attachment is not found apparently-can you reupload?)
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QuentinM
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FEV is usually quoted with a number to indicate the volume of air exhaled over that number of seconds. I'll assume its 4 seconds in this case.

Group A exhales 5L and group B exhales 2.

For percentage difference, its the difference divided by the original value. So in this case, the difference is 3L, and you divide by 5L, giving you 60% decrease from group A to B.
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macpatgh-Sheldon
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Actually, although QuentinM has provided the correct definitions and explanation, the Q states "in the first second", so we need to take FEV1 [which is the value used clinically, incidentally).

So from A to B. there is a reduction from 4.2 to 0.8 = 3.4/4.2 X 100 = 81%

M
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no_this_is_olli
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(Original post by macpatgh-Sheldon)
Actually, although QuentinM has provided the correct definitions and explanation, the Q states "in the first second", so we need to take FEV1 [which is the value used clinically, incidentally).

So from A to B. there is a reduction from 4.2 to 0.8 = 3.4/4.2 X 100 = 81%

M
looked on the markscheme and they say the answer is 19%
not sure how they got that answer?
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macpatgh-Sheldon
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Good morning! (Sorry to bother you while you are dozing away) - you might know that students get up after midday!! .

I think the Q is phrased incorrectly (is this an Edexcel Q?).

When they say %age decrease, it clearly implies how much the REDUCTION is for B compared to A. However, it seems they mean "By what %-age of A is B", which is a COMPLETELY DIFFERENT Q.

So, all they are looking for is: 0.8/4.2 X 100 (by reading the y values off the graph you attached at one second for B and A, respectively) = 19%.

IT IS A WELL-KNOWN FACT THAT at A level Biology you earn max marks by keeping things simple and saying the obvious , BUT THAT DOES NOT MEAN THAT EXAM BOARDS SHOULD BULLY STUDENTS BY ASKING Qs WITH INCORRECT English syntax! :mad:

BTW, are you doing A2 now OR are you at uni?
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ineedsomuchchem
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^^^ just came across this q and i still dont get it?!
(Original post by macpatgh-Sheldon)
Good morning! (Sorry to bother you while you are dozing away) - you might know that students get up after midday!! .

I think the Q is phrased incorrectly (is this an Edexcel Q?).

When they say %age decrease, it clearly implies how much the REDUCTION is for B compared to A. However, it seems they mean "By what %-age of A is B", which is a COMPLETELY DIFFERENT Q.

So, all they are looking for is: 0.8/4.2 X 100 (by reading the y values off the graph you attached at one second for B and A, respectively) = 19%.

IT IS A WELL-KNOWN FACT THAT at A level Biology you earn max marks by keeping things simple and saying the obvious , BUT THAT DOES NOT MEAN THAT EXAM BOARDS SHOULD BULLY STUDENTS BY ASKING Qs WITH INCORRECT English syntax! :mad:

BTW, are you doing A2 now OR are you at uni?
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K_a_m_z
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basically on the graph you look at the time breathing out and go to one second , you then find the values at which the lines hits one second so like group B which is the dotted line is 0.8 at one second and group A which is the bold line is 4.2 you divide them and then multiple to get the percentage so 0.8/4.2 x100 = 19% . Sorry for the rushed reply but thats the basics of how i did it.
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