4.7.2

# Quantitative Investigation

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## 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 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

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

### Standard deviation

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

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