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Random quadrat placement method
Students estimated the population of limpets on a sea shore. The students were given a square quadrat.
Describe one method the students could use to plan where the quadrat should be randomly placed each time.
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Marking points
- 1 Creates a coordinate system or grid over the sea-shore area.
- 2 Selects coordinates using random numbers.
Full-mark answer
Lay two tape measures at right angles to create coordinates for the shore, then use a random number generator to choose a pair of coordinates for each quadrat placement.
Why this answer loses marks
Throw the quadrat without looking.
The official scheme rejects throwing. Map locations with coordinates and use random numbers to select each placement.