A2 Biology | Post your doubts here

[angelgirl:)]

ok could u plz explain a bit about null hypothesis?? evry1 here is giving diferent opinions

Null Hypothesis...it assumes that any kind of difference or significance u see in a set of data is due to chance....and this null hypothesis is rejected if the probibility comes less than 5%....
or for x^2 test...therez no signeficant difference b/w the observed and the expected ratio...

 

[angelgirl:)]

angelgirl:) u left?

lol no.....iam here only

 

[MysteRyGiRl]

Null Hypothesis...it assumes that any kind of difference or significance u see in a set of data is due to chance....and this null hypothesis is rejected if the probibility comes less than 5%....

thnx btw where do we get da probabilty from??

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s09_qp_5.pdf
plz explain where da hell we got 38 from in Q no 3 iv)

dis 1 too plzz
angelgirl:)

 

[angelgirl:)]

also in chi square test if our probability comes out to be greater than 0.05 then its due to chance..what abt t-test??

the same criteria u have to apply for t-test

 

[angelgirl:)]

thnx btw where do we get da probabilty from??

dis 1 too plzz
angelgirl:)

at hourly intervales for 20 hrs so n=20...means (n1-1)+(n2-1)=(20-1)+(20-1)=38...

 

[angelgirl:)]

thnx btw where do we get da probabilty from??

dis 1 too plzz
angelgirl:)

probibility table they will give...for both x^2 as well as t.test

 

[MysteRyGiRl]

at hourly intervales for 20 hrs so n=20...means (n1-1)+(n2-1)=(20-1)+(20-1)=38...

i nvr knew dat btw for t-test degree of freedom will total nmbr of samples minus 2 ryt?

 

[angelgirl:)]

i nvr knew dat btw for t-test degree of freedom will total nmbr of samples minus 2 ryt?

if there r two samples n1=6 and n2=8...so total no. of freedom will be (6+8)-2=14-2=12....

 

[MysteRyGiRl]

if there r two samples n1=6 and n2=8...so total no. of freedom will be (6+8)-2=14-2=12....

haan ok

 

[MysteRyGiRl]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w09_qp_51.pdf
explaination of graph needed inda frst quest?

 

[saad cheema 16]

Okay guys I did a few P5's and here's a tip on all those 8 mark questions which usually ask you to design an experiment.
firstly lets break it up into six portions . Independent variable, dependent variable, controlled variables, procedure, safety and reliability.
No matter how tough the question is dont panic, They dont really expect you to have any background information. 2 marks could be easily scored by telling them to repeat thrice and that 'safety' point. score further two marks by giving two variables that need to be controlled and tell them how you would control them like temp, pH. score one procedural mark ( how you will measure the dependent variable). and score another mark on how u will vary the independent variable. ( another important thing in most questions is to give time to equilibriate). REMEBER this shouldnt be the order of ur answer!!..

 

[angelgirl:)]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Biology (9700)/9700_w09_qp_51.pdf
explaination of graph needed inda frst quest?

the answer is on pg 26

 

[MysteRyGiRl]

the answer is on pg 26

thnx

 

[smartangel]

we repeat experiment for reliability or accuracy? and wider range of concerntrations for?

 

[angelgirl:)]

we repeat experiment for reliability or accuracy? and wider range of concerntrations for?

to add...
for accuracy...=> always some better apparatus...

for reliability => like if u have concentration as independent vaariable, say, take atleast 5 different concentrations....and with each ....repeat at least "three times" [yup not less than that, or u wont get the mark..] , take average, and plot..

this answer is given by user

 

[histephenson007]

Usually what should we write for reliability in those big 8-10 point questions? Like, calculate for the standard deviation, standard error? Can anyone give me a sample paper which includes this plz?!

 

[smartangel]

http://www.xtremepapers.com/papers/...nd AS Level/Biology (9700)/9700_w10_qp_51.pdf
Q1 a ii..plz explain this..i really dont get the experiment..

 

[saudha]

wht do u mean by :in a t-test, "comparing 2 means obtained from 2 samples in a population"
wht kind of 2 samples....give me an xmple sombody>???!!

 

[Paradoxical]

Could someone please upload the mark scheme for Oct/Nov 2011, paper 53? On xtremepapers, it's saying the file is broken. Thanks. ^_^

 

[saudha]

Could someone please upload the mark scheme for Oct/Nov 2011, paper 53? On xtremepapers, it's saying the file is broken. Thanks. ^_^