Classification of technique related to the problem.

To determine monthly rental prices of apartment units in San Francisco Bay area, samples were constructed in the following ways. Identify the technique used to produce each sample. (Cluster, convenience, random, stratified, systematic):

1. Number all the units in the area and use a random number table to select the apartments to include in the sample.

2. Categorize the apartment units according to the number of bedrooms and then take a random sample from each of classes.

3. Order the apartments according to zip code and take a random sample from each of the zip code regions.

4. Look in the newspaper and choose the first apartments you find that the list rents.