Sampling Techniques: Fieldwork and Laboratory Activities

Sampling Techniques: Fieldwork and Laboratory Activities

Sampling Techniques

  • Random sampling: This method ensures every member of a population has an equal chance of being picked. Used to eliminate bias in the selection process and often used in statistical research.

  • Systematic sampling: A chosen system is used to select samples, such as every 10th item. If the population is not biased in a gradient then this method is as good as random sampling.

  • Stratified sampling: The population is divided into strata or subgroups, and random samples are taken from each subgroup proportional to the population of that subgroup.

  • Quota sampling: A number of samples are taken from each subgroup according to the ratio of the subgroups to the total population. It is a non-random stratified method.

  • Cluster sampling: Entire groups or clusters within a population are selected. Useful when dealing with large populations spread over a wide region.

Fieldwork Techniques

  • Transect sampling: Used to study gradients or boundary effects. It involves sampling along a line which could be straight, curved or irregular, depending on the chosen characteristic.

  • Plot sampling: Quadrat, a square frame, is used to define the sample area. Number and distribution of species within each quadrat are recorded.

  • Line intercept technique: Used to study plant populations. A tape measure is laid out and every time a particular type of plant intersects the line it is recorded.

  • Capture, Mark, Release, Recapture (CMRR): Used in wildlife studies to estimate population size. Captured animals are marked then released back into the environment.

Laboratory Techniques

  • Microscopy: Use of microscopes for viewing samples that cannot be seen with the naked eye.

  • Culturing: Growing organisms in a controlled environment to observe their growth, behaviour, reproduction, etc.

  • Chromatography: Used to separate mixtures into their individual components.

  • Spectroscopy: Used to determine the concentration of a substance in a sample, based on how much light the substance absorbs.

Analysis and Recording Techniques

  • Computer modelling: Using computer software to create simulations or models to run tests and make predictions.

  • Graphical representation: Graphs and charts used to visualise data and identify patterns or trends.

  • Mapping: Geographical or spatial data represented on a map.

  • Tables: Tabular representation of data for easy comparison and interpretation.