Citrus trees are usually grown in orderly arrangements of rows to facilitate automated farming and harvesting practices. Suppose a group of 1000 trees is laid out in 40 rows of 25 trees each. To test the sugar content of fruit from a sample of 30 trees, researcher A suggests randomly selecting five rows and then randomly selecting six trees from each sampled row. Researcher B suggests numbering a map of the trees from 1 to 1000 and selecting a random sample (without replacement) of 30 integers from the integers 1 to 1000.

a. Without performing any calculations, do you think that both methods are capable of generating random samples from the block of trees? Justify your answer using the rules for random samples listed in this section.

b. Suppose that the group of trees is grown on the top and sides of a small hill. A researcher suggests that, because growing conditions (e.g., daily amounts of sunlight) are different on the four sides of the hill, the hill should be divided into four quadrants and trees should be randomly sampled from each quadrant. What is the name for this type of sampling procedure?