Random sampling – AQA A Level Biology Summary Notes
Large sample size – ensures sample in representative, allowing anomalies to be identified and thus
allows calculation of reliable mean
Random sample – removes bias from sampling
If taking samples of vegetation, typically a quadrat is used
To ensure sampling method is random, area is usually split into a grid and coordinates are randomly
generated
To decide if enough samples have been taken a running mean of characteristics being measured
should be calculated
When running mean shows little change then enough samples have been taken
Enough samples should be carried for statistical test too
To ensure sampling method is valid, it should be standardised
May involve using same size equipment (quadrats/nets) and samples taken at different locations
should be recorded at same time of day and for same period of time
Describe a typical sampling method to compare something found in two different locations (5 marks)
1. Use random sample
2. Use large enough sample size to be representative
3. Indication of what size was measured eg mass
4. Calculate mean and standard deviation
5. Use a t-test
6. To analyse whether there is a significant difference between ….
Large sample size – ensures sample in representative, allowing anomalies to be identified and thus
allows calculation of reliable mean
Random sample – removes bias from sampling
If taking samples of vegetation, typically a quadrat is used
To ensure sampling method is random, area is usually split into a grid and coordinates are randomly
generated
To decide if enough samples have been taken a running mean of characteristics being measured
should be calculated
When running mean shows little change then enough samples have been taken
Enough samples should be carried for statistical test too
To ensure sampling method is valid, it should be standardised
May involve using same size equipment (quadrats/nets) and samples taken at different locations
should be recorded at same time of day and for same period of time
Describe a typical sampling method to compare something found in two different locations (5 marks)
1. Use random sample
2. Use large enough sample size to be representative
3. Indication of what size was measured eg mass
4. Calculate mean and standard deviation
5. Use a t-test
6. To analyse whether there is a significant difference between ….
