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Quantitative Investigation

Biology: AQA A Level, topic 4.7.2

Investigating Variation

The variation within a habitat can be measured in a quantitative investigation. To ensure the results from the investigation are accurate, the following practices should be used:

Random sampling

Random sampling

  • Random sampling investigates the variation in a population without spending hours counting every individual.
  • Random sampling ensures the sample accurately represents the total variation of the species.
  • Random sampling is applied by assigning individuals numbers and randomly selecting the numbers using a computer program.
Calculating the mean

Calculating the mean

  • The mean provides an average for all the values collected.
  • The mean is calculated in the equation:
  • mean = Σ  allindividualvaluesnumberofvalues\frac{\Sigma \; all individual values}{number of values}
Standard deviation

Standard deviation

  • Standard deviation shows how far away the values are from the mean average.
  • Standard deviation (SD) is calculated in the equation:
  • SD = Σ  (individualvalue−meanforallthevalues)2numberofmeanvalues\sqrt {\frac{\Sigma \; (individual value - mean for all the values)^2}{number of mean values}}

Test yourself on Quantitative Investigation

  • Which of these is NOT a practice used in quantitative investigations?

  • Which of the following statements about quantitative investigations are true?

  • What is the equation for the mean?

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