Scientific investigation
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Define the term accuracy
• the closeness of a measured value to a standard or known value
Define the term precision
• the closeness of two or more measurements to each other
Define the term representative sample
• a sample that represents the whole population
Define hypothesis
• a statement that you test through research and experiments
Define null hypothesis
• type of statistical hypothesis that proposes that no significance exists in a set of given observations
Define random sampling
• type of probability sampling in which the researcher randomly selects a subset of participants from a population
Define systematic sampling
• a probability sampling method where researchers select members of the population at regular intervals
Define stratified sampling
• involves the division of a population into smaller subgroups
What should you consider when deciding the number of samples in a study
• size of population -variability in population
What is a standardised sampling method and why is it important
• method that allows data to be collected in exactly the same way by different people at different times • give clear methods and equipment • control any variables
Why is timing important in experimental design
• time of day, night • if organisms have a life cycle e.g hibernation • migration patterns
What is a belt transect
• sample along a route at regular intervals
What is an abundance scale and why are they useful
• way of applying what you see to a category • doesn’t require counting
What are the limitations of an abundance scale
• subjective • no statistical tests • relies on human observations ( room for error )
What are the 3 types of quadrats
• open frame • grid -point
What is kick sampling and what are the limitations
• hold a net downstream and disturb the bed of water and collect sediment in net • different efforts put into kicks -some organisms can swim
What is suber sampling and what are the limitations
• same as kick sampling but with a frame on where you kick • ground could be uneven
What is colonisation media and what are the limitations
• provide a habitat for the organism that you’re counting • organism isn’t attracted to it • don’t have total population size
What is a pitfall trap and what are the limitations
• dig a hole and place a cup in the ground and insects will fall into it • some could escape • organisms could eat one another
What is a sweep net and what are the limitations
• sweep a net in a figure of 8 to catch things such as moths in a large field • organism could be harmed • organism could escape
What is a beating tray and what are the limitations
• beat a huge net underneath a tree and invertebrates will fall and land on the tray • organisms can fly • organisms could remain in the tree
What is a light trap and what are the limitations
• using uv, white light to catch moths • could escape before counting • different species of moth are attracted to different wavelengths of light
What is a tullgren funnel and what are the limitations
• collect a soil sample, and it filters down the tunnel and organisms are caught in a dish at the bottom • heat may harm the organisms • some organisms may be too big to filter all the way down
What is earthworm extraction and what are the limitations
• add an irritant, water or stamp on the ground to attract the worms upwards • irritant could kill the worms -worms could move sideways instead of upwards