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*Biology Paper 5 tips*

A

Amaryllis

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Marks&Spencers said:
Regarding table 3.1, if you're wondering about how to complete the expected values, then look at page 8 of this thread. Someone had already asked this question and it was answered. Other than that, the rest of the columns just involve simple calculations.
I agree with you, sometimes that whole degrees of freedom thing can be really annoying, and to be honest I'm not still 100% sure I managed it perfectly or not, but from what I understood from doing past papers, when you're dealing with a x2 test, you look at the number of phenotypes/categories that you look at their expected and observed values, then minus one from that number. In that question, for example, there were 3 categories: grazed for 2 years, ungrazed for 10 years and ungrazed for 30 years. Degrees of freedom would therefore be 3-1=2.
When you're dealing with t tests, you look for the number of samples taken to calculate each mean, minus 1 from each, then add them together. For example, if they tell you that they obtained 10 leaves, measured the surface area of each and obtained a mean for their values, then brought another 10 leaves from a different plant, measured the surface area of each, and obtained a mean for their values. When you compare these 2 means (using a t test), the degrees of freedom would be (10-1) + (10-1) = 18.
Remember, the rule is (n-1). I hope you got it!
(Someone please correct me if I'm wrong, or add information I missed out on.
Click to expand...

thank you so much :) this is really helpful
 
D

dornam

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So what are the main experiments we should focus on for tomorrow? Is there any point in studying the practical booklets?
 
Student12

Student12

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i at times don't get the independent and the dependent variable right.. If anyone could explain ?
Iknow
  • Independent Variables are changes that occur in an experiment that are directly caused by the experimenter (you.)
  • Dependent Variables are changes that occur due to independent variables.

    But when it comes it doing the questions i often get it wrong..
    SOMEONE ?
 
knowitall10

knowitall10

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Student12 said:
i at times don't get the independent and the dependent variable right.. If anyone could explain ?
Iknow
  • Independent Variables are changes that occur in an experiment that are directly caused by the experimenter (you.)
  • Dependent Variables are changes that occur due to independent variables.

    But when it comes it doing the questions i often get it wrong..
    SOMEONE ?
Click to expand...
Whatever you're testing for will be the dependant variable. Say for Effect of Light on the rate of Photosynthesis. the rate of photosynthesis is what you're testing-it's the dependent variable. But what are you testing it with? Light. So light will be your independent variable.
 
Student12

Student12

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knowitall10 said:
Whatever you're testing for will be the dependant variable. Say for Effect of Light on the rate of Photosynthesis. the rate of photosynthesis is what you're testing-it's the dependent variable. But what are you testing it with? Light. So light will be your independent variable.
Click to expand...

Some more examples?
 
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