Task 2: Intensive agricultural practices often include the use of pesticides to enhance yields. However the improvement in yield s sometimes associated with the occurrence of pesticide residues in soil. Researchers were interested in the pesticide levels in the soil in four areas that were used for dairy production. Each area was divided into grids of 300 rectangles and a number is assigned to each rectangles. A- random sample of 50 rectangles is taken in each area. Each of the chosen rectangles is further divided into 100 one metre squares and 20 random soil samples are taken. The 20 soil samples are thoroughly combined and the combined sample for each selected rectangle is used to give an estimate of the concentration of the pesticide residue in the soil in each area. (a) Why do you think that the combined soil sample was analysed rather than a single soil sample from each rectangle? (b) Name the types of sampling that were used in the stud to obtain the sample. (C) Are the results likely to be representative of the population of interest? Give reason answer.
a)
As first the area was divided into grids of 300 rectangles and a sample of 50 such rectangles were choosen, and these 50 rectangles were further divided into 100 one metre squares. So to get the concentration of pesticide in each of the 50 samples taken initially, these 20 soil samples are combined.
b)
The sampling is random, When initially the area is divided into 300 rectangles and 50 rectangles were taken, the choice of choosing was random, and then each rectangle is divided into 100 one metre squares and 20 such squares are taken, the process is again, random
c)
Since whole area is divided into 300 rectangles, and 50 such rectangles are choosen at random, So the result can represent the population of interest,. Because these 50 rectangles can be any of the areas part.
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