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Biology Higher Twilight 2

Experimental Design Questions

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  • Paper design brief says expect an experimental design question 5-9 marks
  • In that question you will be commonly asked to
    • Identify independent variable
    • Give controlled variables not mentioned already
    • Design a control
    • Draw conclusion
    • Give evaluation points
    • Draw a graph of the data

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Variable – something that can change

  • Splits into three kinds in an experiment
  • Independent Variable
    • The variable in the experiment that we change so we can study what impact it has
  • Dependent Variable
    • The Variable that we measure (it depends on what happened during the experiment)
  • Controlled Variables
    • All the variables that have to be kept under control so they cannot change the result (NOT the independent)

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Words to look for and use correctly!

Reliable (Most likely to come up)

Reliable means you can trust the answer

So to increase reliability you repeat the experiment.

This gives you a more reliable average not more accurate.

Accurate

Might be used by you in an evaluation point.

It means that your measurement is more precise e.g. measuring in centimeters rather than meters

You may also be able to shift from human to tech for taking a result e.g. you deciding on colour change, using a colorimeter

Valid (unlikely to use, but may be in question)

Valid means it was the right measurement to make

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What is a control?

  • The most useful word in controls is compare
  • You set up an experiment exactly as your test experiment, but with the thing you think is causing the result removed e.g. kill yeast cells by boiling or remove entirely
  • A control gives you a result to compare your test results to and so be certain it is the independent variable that is causing the result.

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What was

changed

What you measured

Or use the nappy rule – what you change goes across the bottom

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Graphs

  • Extra bits to check for
    • Check marks – use them all!
    • ½ scale x and y
    • Origins on BOTH axes on a line graph (avoid the single zero)

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Experimental Design Questions

  • 2007 Q10
  • 2008 Q11
  • 2009 Q10
  • 2010 Q10 (not e)
  • 2011 Q10
  • 2012 Q4
  • 2013 Q4
  • 2014 Q12
  • 2015 Q5
  • 2015 CfE Q3
  • 2016 CfE Q11
  • 2017 CfE Q9
  • 2018 CfE Q10
  • 2019 CfE Q12