A student samples heather plants on an area of heathland using equal-sized quadrats.
For Sample A, the student places eight quadrats at random.
For Sample B, the student places eight quadrats where the heather appears most dense.
| Sample | Numbers of heather plants in the eight quadrats |
|---|---|
| A | 1, 2, 1, 3, 2, 4, 1, 2 |
| B | 3, 5, 4, 6, 2, 4, 3, 5 |
The student uses Sample B instead of Sample A to estimate the number of heather plants in the same area.
Which statement correctly describes the effect of using Sample B?
Sample B gives an estimate 16 plants larger than Sample A, and this estimate is biased because the quadrats were not placed at random.
Sample B gives an estimate twice as large as Sample A, and this estimate is more accurate because more heather plants were counted.
Sample B gives an estimate twice as large as Sample A, and this estimate is biased because the quadrats were not placed at random.
Sample B gives an estimate 16 plants larger than Sample A, and this estimate is more accurate because more heather plants were counted.
83 exam-style questions on AQA GCSE Biology 7.2 Organisation of an ecosystem, covering 7.2.1 Levels of organisation, 7.2.2 How materials are cycled, 7.2.3 Decomposition, and 7.2.4 Impact of environmental change (HT only). Each one has a worked solution and a mark scheme showing where the marks go.