5 original questions · Application and evidence

Ecological sampling: estimates and causation

Use the context and data to draft a response, then compare your reasoning with an explanatory example.

Context and data

Eight non-overlapping 0.50 m² quadrats were placed at randomly selected positions across a 2000 m² field. A plant count and soil-moisture reading were recorded at each position. The field boundary defines the sampling area.

Independent quadrat observations
Quadrat	Plant count	Soil moisture / %
1	2	20
2	0	15
3	5	35
4	1	22
5	4	32
6	0	18
7	3	30
8	1	25

Original illustrative data. Use the stated assumptions and units; these are not examination-board questions.

This worksheet includes questions and data, with space for your responses. Answers are omitted.

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Ecological sampling: estimates and causation

Context and data

Five questions

1. Calculate mean plants per quadrat, estimated mean density and estimated total plants in the field.

2. Describe the relationship between the supplied moisture readings and plant counts, using evidence while allowing for variation.

3. Evaluate the claim that increasing moisture alone would cause the same increase in plant abundance shown by the table.

4. Why is random quadrat placement appropriate for a whole-field mean, and how would the design change to investigate a pattern along a slope?

5. Suggest an improvement to the abundance estimate and explain what uncertainty it addresses.