Edexcel 6bi07 (unit 3) on 06th may 2014

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Consider the table from GCE biology unit- 3B May 2011 1(c)
Notice that the value in row 5's Mean tensile strength is 1074 MPa. The SD stated for the value is 185 MPa. If you subtract the SD from the mean value you get 889 MPa which overlaps with the value in row 4's mean (916 MPa) with its SD added or subtracted to it.
Overlapping SDs are usually considered as unreliable. Large SDs alone are unreliable too. THe smaller the SDs, the better the reliability.
Hope this helps you a little. :smile:

Woahh,Omg,thank you sooo much for explaining soo amzingly! :-* ! Helps loads :smile:

Reply 41

Lassy96

Tip: Guys referencing is very important,comes in every paper, improve on that and we'll secure 1-2 marks :smile:

Reply 42

Lassy96

help! question 1d(iv) for May 2013 paper 3B! How to ans the question?
This is what the MS says :

1. Idea that because there is a (l
arge / small) difference in the
means (linked to the relevant pair) ;

0.5 and 0.9

2. credit use of SD data and ref to no overlap ;

0.3 and 0.5

3. credit recognition of fact that some figures for 0.3 mm are
the same as some for 0.5 mm (n
amely 8.9) or very close ;

4. credit use of SD data and ref to do overlap;

For either

5. credit manipulation of figure
s to calculate upper and lower
limits e.g. (0.5 mm lower limit 7.5, 0.9 mm upper limit 4.3,
0.3 mm lower limit 8.3 , 0.
5 mm upper limit 8.5 / OR
comment on 0.8 SD ;

Reply 43

sorabackwards

I need help in validity, reliability and improvements on source type questions

also in the graph, it says u must include Standard deviation. how do i do that?

thanks

Reply 44

sorabackwards

guys I need help in validity, reliability and improvements on source type questions

also in the graph, it says u must include Standard deviation. how do i do that?

thanks

exam is tomorrow :smile:

) il be doing it here in the UAE. wat about you guys?

Reply 45

Bimbo97

guys.. in the mineral deficiency experiment,, why do we cover the test tubes with aluminium foil or black paper?

Reply 46

Bimbo97

Original post by sorabackwards

guys I need help in validity, reliability and improvements on source type questions

also in the graph, it says u must include Standard deviation. how do i do that?

thanks

exam is tomorrow :smile:

) il be doing it here in the UAE. wat about you guys?

I can help with the standard dev bit :P
u plot the graph with the mean values obtained. then you need to find the upper and lower limits i.e get the max number for that set and locate the point on the graph and join it to the mean. Then locate the lowest value on graph and join it t the mean. this gives youth S.D bars.

Reply 47

sorabackwards

Original post by Bimbo97

) hahaha i saw an example too (y)

Reply 48

sorabackwards

Original post by Bimbo97

guys.. in the mineral deficiency experiment,, why do we cover the test tubes with aluminium foil or black paper?

you wrap it with aluminum foil and place it in a tube holder on sunny windows sill. i think the reason for this is to retain the heat absorb which is why the foil is used to cover the whole tube. i may be wrong but this is waht i think :smile:

Reply 49

Miffyy

In finding environmental implications you have to search for something to do with the environment, eg: loss of biodiversity.
Social implications are related to the people or society and how it benefits or not benefits them

Reply 50

Miffyy

Original post by Paras Agarwal

guys here are some amazing bio notes for the unit 3 paper coming in 2 days! http://www.scribd.com/doc/112086888/List-of-Core-Practicals-for-Edexcel-Biology

That's Stafford Valentine Redden's book. He sells them on amazon, so you can buy it from there. I learn for biology using his books and he's also my teacher :smile:

Reply 51

sorabackwards

any last minute tips to prepare? exam is tomorrow :frown:

ive been doing past papers and ive gone thru all the experiments

Reply 52

Sea Panda

Original post by saifulahmed

hey what's the format of writing a bibliography?

Book: Author, Initials, Year, Title, Edition (If not first edition), Place of publication
Journal: Author,Initials, Year, volume number, Page numbers
Website: Authorship or source, Title of article, Available at:

Reply 53

Ripper Phoenix

Original post by sorabackwards

I need help in validity, reliability and improvements on source type questions

also in the graph, it says u must include Standard deviation. how do i do that?

thanks

hi..saw ur post on my profile..well here is an answer for all!
validity and reliability always look for standard deviations if they are given.. now check if they are large or small.. if they are large the data is unreliable hence the smaller the sd's the more reliable the data.. for validity all variables must be kept constant!

um..your question on source type questions? could u please give an example?

Lastly to plot standard deviations: you will always be given a mean from the table.. from the mean you add the standard deviations above and below the mean more like + or - eg 5 so u plot 5 units above and below the mean!! :smile:

Reply 54

Sea Panda

Original post by Bimbo97

guys.. in the mineral deficiency experiment,, why do we cover the test tubes with aluminium foil or black paper?

Black paper: to prevent light from entering the solution, so that aquatic photoautotrophs would not compete with the seedling roots for minerals.

Reply 55

Ripper Phoenix

anybody feeling the pressure noww?? :biggrin:

Reply 56

sorabackwards

Original post by Paras Agarwal

its alright i got the source question cleared up. however heres a question on jan 2012 bio 3b.

concerning the comparison of vitC in fruit and vegetables, the question is:

compare these data with those that the student obtained in her study and comment on the validity of her results.

so how do i tackle that question? :smile:

ty so much

Reply 57

sorabackwards

Original post by Paras Agarwal

anybody feeling the pressure noww?? :biggrin:

hahah i feel it :P my exam is in the morning. i have 20 hours left hahah