CH11 types of sampling Flashcards
1
Q
What is sampling
A
- taking measurements of a limited number of individual organisms present in a particular area
2
Q
Why is sampling useful
A
- can be used to estimate the number of organisms in an area without having to count them all
- can measure a particular characteristic of an organism
3
Q
Random sampling
A
- selecting individuals by chance, so each individual has an equal chance of selection
- random number tables or computers are used
4
Q
Non-random sampling
A
- sample chosen not at random
- divided into three groups: opportunistic, stratified and systematic
5
Q
Opportunistic sampling
A
- uses organisms that are conveniently available
6
Q
Stratified sampling
A
- populations divided into a number of strata based on particular characteristic
- random sample is taken from each of these strata proportional to its size
7
Q
Systematic
A
- different areas within an overall habitat are identified, and are then sampled seperately
- may be used to see how plant species change as you move inland
8
Q
Line transect
A
- involved marking a line along the ground between two poles and taking samples at specified points
9
Q
Belt transect
A
- provides more information
- two parallel black lines are marked, and samples taken of the area between the two lines
10
Q
Why is sampling not always reliable
A
- sampling bias
- chance, not representative
