Different Sampling Types

Question 1

Describe random sampling

Answer 1

1) mark out a grid with two tape measures laid at right angles
2) use random number generator to determine the coordinates
3) take sample at each of the coordinates generated and compare with other

Question 2

Describe opportunistic sampling and when used

Answer 2

1) time or resources are limited
2) new research method

Least accurate and quickest method

Question 4

Describe stratified sampling

Answer 4

1) some populations are divided into a number of strata based on characteristics
2) random sample is taken from strata proportional to its size

Question 5

Describe systematic sampling

Answer 5

1) different areas within same habitat which are sampled separately with line transect
2) line transect marks a line along the ground between two poles and then able to measure population between the poles

Question 6

How to sample animals

Answer 6

1) pooter -
2) sweep nets- in areas of long grass
3) pitfall traps- hole is dug into ground which insects fall into deep enough so they can’t crawl out and covered
4) tree beating- tree is shaken to dislodge insects from tree and falls onto white sheet underneath

Question 7

How to sample plants

Answer 7

1) point quadrat- consists of frame containing horizontal bar
2) frame quadrat

Question 8

Reasons for maintaining biodiversity

Answer 8

1) aesthetic- prescence of different plants and animals enrich our lives
2) economic- promotes tourism so more profit.
3) ecological- all organisms indterdependent on others so removal of one species may affect others, for example bees rely on plants for pollen

Question 9

What is keystone species

Answer 9

• species that play a role in maintaining structure of an ecological community
• has a disproportionally large effect on environment

Question 10

Advantages of random sampling

Answer 10

• Easy to implement
• Free from bias
• Each member of population equal chance of being chosen

Question 11

Disadvantages of random sampling

Answer 11

• complete list of population may not be available
• least accurate as minority subgroups may not be present

Question 12

Advantages of stratified sampling

Answer 12

• strata can be proportionally represented in final sample
• easy to compare groups

Question 13

Disadvantages of stratified sampling

Answer 13

• information must be gathered before to divide into subgroups

Question 14

Advantages of systematic sampling

Answer 14

• easy to select
• easy to identify
• evenly spread over entire population

Question 15

Disadvantages of systematic sampling

Answer 15

• may be biased where pattern is used