6.1 For each of the following situations, define an appropriate random variable and state whether it is continuous or discrete.

a An environmental engineer is looking at 10 field plots to determine whether they contain a certain type of insect.

b A quality-control technician samples a continuously produced fabric in square-yard sections and counts the number of defects she observes for each sampled section.

c A metallurgist counts the number of grains seen in a cross-sectional sample of aluminum.

d The metallurgist of part

(c) measures the area proportion covered by grains of a certain size rather than simply counting them.