After a hurricane, a disaster area is divided into 200 equal grids. Thirty of the grids are selected, and every occupied household in the grid is interviewed to help focus relief efforts on what residents require the most. The sampling technique used is:. A) Stratified Sampling.
B) Cluster Sampling.
C) Systematic Sampling.
D) Simple Random Sampling.

B) Cluster Sampling.

Step-by-step explanation:

Cluster sampling refers to a methodology for probability sampling, in which researchers split the populace into several study groups or one can say clusters. And after this investigators pick random groups for collecting and analyzing data, using a systematic random or simple random sampling technique, depending on the research subject. As per the question, instead of 200 grids selected a cluster of 30 grids for the research and therefore it is a classic of cluster sampling.

true statements:

a) x + y = y + x   ⇒ commutative property of addition

b) (x * y) * z = x * (y * z) ⇒ associative property of multiplication

d) (x + y) + z = x + (y + z) ⇒ associative property of addition

false statements:

c) x - y = y - x   should be: x - y = - y + x

e) (x - y) - z = x - (y - z) should be: (x - y) - z = x - (y + z)

step-by-step explanation: