Biology Paper 6 (6BI08) 2012 Official

doc 2.doc
chi-squared test.docx

OP

Reply 3

aqua05

9

awww bless you demdil :biggrin:

You're amazing :biggrin:

Reply 4

i just wish ecological sampling doesnt come , im beginning to hate it
ok anyway can someone explain to me how is 0.05 somewhere 5% significance level and somewhere 95% confidence level ??! and why does it even matter ??!

Reply 5

i just wish ecological sampling doesnt come , im beginning to hate it
ok anyway can someone explain to me how is 0.05 somewhere 5% significance level and somewhere 95% confidence level ??! and why does it even matter ??!

Reply 6

also i think that mark schemes are very similar from year to year , for example in the question asking for some preliminary work (4 marks)we can write :_
- independent variable
- how to control that
- dependent variable
- how to measure that
- practice method beforehand
- choose a timescale to record/measure the dependant variable
- find out most suitable conditions for the experiment and try to execute them when experimenting !

someone else please share more ideas like this !!! not much time left now !! can feel the nerves ....!

Reply 7

OP

Original post by iesians

i just wish ecological sampling doesnt come , im beginning to hate it
ok anyway can someone explain to me how is 0.05 somewhere 5% significance level and somewhere 95% confidence level ??! and why does it even matter ??!

i only know that in biology they always use 0.05 significance level, and that means they are 0.05(5/100) unsure and 0.95(95/100) sure. So the conclusions drawn are always at 95% confidence level(they are 95% sure).. I dont know if i explained well, because i think its about statistics and i never took any statistics lesson :/ .. hope i helped..

Reply 8

OP

Original post by aqua05

awww bless you demdil :biggrin:

You're amazing :biggrin:

thanks

these are from previous paper 6 threads but i only collected them and posted them here. so we can have our own thread and ask each other questions and help each other :smile:

.. i'd be happy if anyone finds other resources or anything about paper 6 from either TSR or somewhere else and share with us :smile:

..

Reply 9

Original post by demdil

thanks

these are from previous paper 6 threads but i only collected them and posted them here. so we can have our own thread and ask each other questions and help each other :smile:

.. i'd be happy if anyone finds other resources or anything about paper 6 from either TSR or somewhere else and share with us :smile:

..

i wanted to ask a question .... how can we know from data if v have to use spearman rank or T test ??! and anyway i know spearman is for finding out a correlation .....what is T test for ??! or it just tells or if null hypothesis is correct or not ....?!

Reply 10

OP

Original post by iesians

i wanted to ask a question .... how can we know from data if v have to use spearman rank or T test ??! and anyway i know spearman is for finding out a correlation .....what is T test for ??! or it just tells or if null hypothesis is correct or not ....?!

t-test is for comparing two groups. in t-test, if the calculated t-value(given in the question) is greater than the critical value given in the table, we reject the null hypotesis and conclude that there is a difference between our two groups.

Reply 11

Original post by demdil

t-test is for comparing two groups. in t-test, if the calculated t-value(given in the question) is greater than the critical value given in the table, we reject the null hypotesis and conclude that there is a difference between our two groups.

comparing two groups ?? can you clarify it a bit more ...... we compare two groups in what sense , to know correlation or what ??!

Reply 12

OP

Original post by iesians

comparing two groups ?? can you clarify it a bit more ...... we compare two groups in what sense , to know correlation or what ??!

i'Ll try.. i can give some examples; t-test is when we compare the heights of plants in two different ecological areas, or comparing masses of two groups of students(this was on one paper, one group of students had breakfast regularly, the other group didnt) and t-test is not for correlation, its for comparison, to see the difference in mass/height etc. between two groups. Also you can decide whether or not to do a t-test by looking at the data, if the data has at least 30 values and if data is normally distributed then you carry out t-test. (remember from unit 2 biology; normal distribution etc) eg. height is continuous data so normally distributed therefore t-test ..

if its like different concentrations of something on another variable -> not continuous as we know the concentrations (if its 5%, or 15%, its clear) and that means we're looking for correlation between the two.

so; if normally distributed data with more than 30 values present, and two groups are compared -> t-test
if discrete data(5% concentration) and like 5-10 values present(eg. 5 different concentrations used) and two variables given -> then spearmans rank correlation.

english is my second lang. and i dont know if i explaned well but i hope i did :smile:

Reply 13

Original post by demdil

i'Ll try.. i can give some examples; t-test is when we compare the heights of plants in two different ecological areas, or comparing masses of two groups of students(this was on one paper, one group of students had breakfast regularly, the other group didnt) and t-test is not for correlation, its for comparison, to see the difference in mass/height etc. between two groups. Also you can decide whether or not to do a t-test by looking at the data, if the data has at least 30 values and if data is normally distributed then you carry out t-test. (remember from unit 2 biology; normal distribution etc) eg. height is continuous data so normally distributed therefore t-test ..

if its like different concentrations of something on another variable -> not continuous as we know the concentrations (if its 5%, or 15%, its clear) and that means we're looking for correlation between the two.

so; if normally distributed data with more than 30 values present, and two groups are compared -> t-test
if discrete data(5% concentration) and like 5-10 values present(eg. 5 different concentrations used) and two variables given -> then spearmans rank correlation.

english is my second lang. and i dont know if i explaned well but i hope i did :smile:

wow ! u explained that part like a pro !! loved it !! thank you so much !! best of luck for exam .....share more stuff , techniques , strategies , .....

Reply 14

cisne

UNIT 6B

QUESTION 1
part ( a )
:: Experiment procedure (5marks)

procedure
control
repetition of the experiment
measuring the data
variables(dependent/independent)
controlling variables
safety measures

part ( b )
:: related to variables
dependent/independent
eg)name a variable (related to the procedure given)

part ( c )
:: how can we control that variable
:: if not controlled what will be the effect (effect on dependent variable)

part ( d )
:: (factor given i the question)if not controlled what will be the effect
(total 9 marks)

QUESTION 2
part ( a )
:: null hypothesis(negative of the statement given)

part ( b )
:: ethical reason

part ( c )
:: Calculation of mean

part ( d )
:: preparation of the table
: table format should be suitable
: correct column/rows with accurate headings
: calculate mean
: correct values

part ( e )
:: graph
: suitable graph
: axes labelled with correct unit
: correctly plotted values

part ( f )
: correlation coefficient

(total 16 marks)

Some clues.....Hope for the best.....

(edited 11 years ago)

Reply 15

verdikt

That's all fine, but what do we mention when it comes to writing electrophoresis and PCR? Is that even possible for it to come in the first question?

Also I always learnt it as T-Test = bar graph and Spearman = scatter graph. Is this wrong?

Reply 16

OP

Original post by verdikt

That's all fine, but what do we mention when it comes to writing electrophoresis and PCR? Is that even possible for it to come in the first question?

Also I always learnt it as T-Test = bar graph and Spearman = scatter graph. Is this wrong?

PCR and electrophoresis may come as first question but not as third. But i dont know what do we have to mention :/
t-test-> bar chart/ histogram
spearman-> line graph/ scatter diagram is okay :smile:

Reply 17

verdikt

Original post by demdil

PCR and electrophoresis may come as first question but not as third. But i dont know what do we have to mention :/
t-test-> bar chart/ histogram
spearman-> line graph/ scatter diagram is okay :smile:

Exactly. Every book is pretty vague when it comes to this. Can someone please shed a light on what comes for electrophoresis/PCR?

Also demdil, please check inbox :smile:

Reply 18

Original post by verdikt

Exactly. Every book is pretty vague when it comes to this. Can someone please shed a light on what comes for electrophoresis/PCR?

Also demdil, please check inbox :smile:

ok emme give a good try :-
CLUELESS ABOUT ELECTROPHORESIS !!

PCR :- mix the original DNA sample into a PCR machine which is already filled with DNA polymerases , DNA primers and all the four nucleotides .
first heat the mixture at 95C , this will break the hydrogen bonds between the orginial DNA strands .
cool till 45 - 50C , at this temperature DNA primers will attach to specific regions on the strands of DNA.
bring the temperature to about 75C , as this is the optimum temperature for DNA polymerase catalysis !
repeat this cycle about 20-30 times to get innumerable DNA strands similar to the original sample !

i think PCR wont come cuz it came in jan 2012 bio unit 4 ....hmmmm

Reply 19