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the theory or explanation that is being investigated.
(states that a relationship exists)

Independent Variable (IV)

the factor that is deliberately altered or measured to see if it affects the dependent factor

Dependent Variable (DV)

the factor that may be controlled by the IV, i.e. the 'results' that are measured

Null Hypothesis

the no-link theory against which the hypothesis is being tested.
(states that there is no relationship)

Random sampling

the sampling sites within the study area can be chosen using a table of random numbers, or the random number function of a scientific calculator, to select coordinates on a grid

Systematic sampling

this involves samples taken using a chosen pattern or spacing. (it can be considered to be random in that the samples are not chosen based on observable differences in the study area)

Stratified sampling

if a study area has clear sub-areas with differences that will influence the results then it may be necessary to study each area individually, then combine the results


evenly mixed


an area, usually square or circular, in which samples are taken

Pitfall trap

a method of sampling animal populations by collecting individuals that fall into traps set into the ground


a line or belt of sampling sites across an area

DAFOR abundance scale

a qualitative scale that judges the abundance of organisms:
D = dominant
A = abundant
F = frequent
O = occasional
R = rare

Lincoln index

a catch, mark, release, recapture method of estimating animal populations:
Total Population = No. in 1st sample x No. in 2nd sample / No. in 2nd sample that have marks

Kick sampling

the riverbed is disturbed by kicking so that mobile invertebrates are washed into a net downstream

Surber sampler

an aquatic invertebrate sampling frame and net that provides more quantitative data than kick sampling


a mouth-suction device to pick up invertebrates in soil or leaf litter

Sweep Nets

lightweight newts with large diameter that can be swept through vegetation to collect invertebrates.
If number and length of the sweeps are standardized then semi-quantitative data can be collected.

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