In cluster random sampling, the population is first divided up into mutually exclusive and collectively exhaustive groups, called clusters. A cluster sample includes randomly selected observations from each cluster, which are proportional to the cluster’s size.

a. True.
b. False.

The statement provided is True.

Step-by-step explanation:

Cluster Sampling is a method to randomly select samples from a population that is too enormous for simple random sampling.  

Using cluster sampling, the experimenter first distributes the entire population into distinct groups, called clusters. These clusters are mutually exclusive and collectively exhaustive, i.e. none of the values is repeated.

Then a simple random sample of clusters is chosen from the population.

The size of the sample selected from each cluster is proportional to the size of the clusters.

Then the experimenter performs the analysis on the data from the sampled clusters.

Thus, the statement provided is True.

225x²+4=0

225x²=0-4

225x²=-4

x²=-4/225

x=±√-4/225