Non-Random Sampling

The sample may not be chosen at random.There are three main types of non-random sampling:   Opportunistic Sampling   Stratified Sampling   Systematic SamplingOpportunistic sampling may not be representative of the population as any organism that is conveniently available is used.Stratified sampling involves taking a random sample from each stratum or subdivision. The subdivisions are based on a particular characteristic.The number taken from each stratum is proportional to the size of the stratum.In systematic sampling different areas within an overall habitat are identified and samples are taken from each area.A line transect involves marking a line along the ground between two poles and taking samples at specific points. This can include counting all organisms that touch the line.A belt transect uses two parallel lines and places a quadrat between the line to sample the areas at regular intervals along the transect.