A level Biology: Post your doubts here!

[Mairaxo]

Yes i know,those are two questions.
how do we solve question 3b AND how do we know that the t test was for the tubule diameter and not for the diameter of the lumen?

yeah they didnt specify but i dont think it really mattered as we could solve without knowing for b u just have to give reasons why its reliable. many measurements were taken etc. however the brush border of columnar cells werent measured so that would make it unreliable

 

[Noor Ahmad]

yeah they didnt specify but i dont think it really mattered as we could solve without knowing for b u just have to give reasons why its reliable. many measurements were taken etc. however the brush border of columnar cells werent measured so that would make it unreliable

In the examiners report it was mentioned.
I just don't get it

 

[freezingfires]

Can somebody explain that in Winter 2008 paper 5 (question 2 b,iv) why cant we take t values when probability=0.01 while finding the solution to the ans?
I'd be grateful if someone gave me a detailed explanation!!

 

[Mairaxo]

In the examiners report it was mentioned.
I just don't get it

hmm i dont get it either! it was more simple in the mark scheme!

 

[Noor Ahmad]

hmm i dont get it either! it was more simple in the mark scheme!

Thank youu anyway.It was until i opened the er.

 

[Mairaxo]

Can somebody explain that in Winter 2008 paper 5 (question 2 b,iv) why cant we take t values when probability=0.01 while finding the solution to the ans?
I'd be grateful if someone gave me a detailed explanation!!

we always take 0.05 in chi square and t-test. in the text book it was written about 0.05 being scientifically proved or something. so just always use 0.05 value

 

[freezingfires]

we always take 0.05 in chi square and t-test. in the text book it was written about 0.05 being scientifically proved or something. so just always use 0.05 value

Thanks! ok that is fixed always gotta take 0.05!

 

[Mairaxo]

Thanks! ok that is fixed always gotta take 0.05!

yuppp (Y)

 

[Mairaxo]

May 2012 52 .. 2b)ii) is 400% in the mark scheme! but im getting 300% :/

 

[Soldier313]

they didnt mention it but its always supposed to be going downwards

Owh really ? :O I never knew that :/

Q2- find the mean of both. before coffee=0.1725 after coffee=0.1525 subtracting them u get 0.02. then 0.02/0.1725*100 u get 11.59 thats almost 12%

Thanx a lot

 

[Soldier313]

Guys can you please help me with question 3b.?
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s08_qp_5.pdf

how do we know that the t-test was done for the tubule diameter and not for the diameter of the lumen?

I don' t get it either

 

[Mairaxo]

how to calculate % increase? For example population was 1st 20 and then it became 50. so it will be 50/20*100 giving 250. do we have to subtract 100 from 250? or will the % remain 250%?

 

[Soldier313]

how to calculate % increase? For example population was 1st 20 and then it became 50. so it will be 50/20*100 giving 250. do we have to subtract 100 from 250? or will the % remain 250%?

it will be [ (50-20)/20 ] x 100 %

 

[Mairaxo]

it will be [ (50-20)/20 ] x 100 %

Thats % difference not increase solve it in May 2012 52 q2bii)

 

[gary221]

how to calculate % increase? For example population was 1st 20 and then it became 50. so it will be 50/20*100 giving 250. do we have to subtract 100 from 250? or will the % remain 250%?

subtract from 100 --> 250 - 100 = 150%
i do it this way,
for %increase, u first find the increase in population.
ie from 20 ----> 50, so increase = 30
now the increase divided by the original population. ---> 30/20 * 100 = 150 %

All credit to Nibz

 

[Mairaxo]

it will be [ (50-20)/20 ] x 100 %

oh okay i got the same answer but in a diff method but still let me know what u got in that qstn!

 

[Irfan1995]

May 2012 52 .. 2b)ii) is 400% in the mark scheme! but im getting 300% :/

The percentage increase would be 300%, but that's not what they're asking for.
They wanted the RELATIVE increase. If you have a 40% sodium chloride solution, that would be eight times as concentrated as a 5% solution, but only a 700% increase. The relative increase would be considered 8 (which is 40/5) rather than (40-5)/5 = 700%.
Going back to the question, you have the value at 60 degrees being 56 and at 50 degrees is 14.
The relative increase is simply 56/14 = 4

 

[Mairaxo]

subtract from 100 --> 250 - 100 = 150%
i do it this way,
for %increase, u first find the increase in population.
ie from 20 ----> 50, so increase = 30
now the increase divided by the original population. ---> 30/20 * 100 = 150 %

All credit to Nibz

thanx! i do it the 1st way as wel but my answer doesnt match the one in the mark scheme!

 

[Mairaxo]

The percentage increase would be 300%, but that's not what they're asking for.
They wanted the RELATIVE increase. If you have a 40% sodium chloride solution, that would be eight times as concentrated as a 5% solution, but only a 700% increase. The relative increase would be considered 8 (which is 40/5) rather than (40-5)/5 = 700%.
Going back to the question, you have the value at 60 degrees being 56 and at 50 degrees is 14.
The relative increase is simply 56/14 = 4

so how did the 400% come?

 

[Irfan1995]

so how did the 400% come?

4 = 4 x 100% = 400%

Or you could have just done (56/14) x 100% = 400%