Interviewer instructions
<span class="h1">4.3 Selection units</span>
<br />The following are the concepts related to selection units:</p>
<p><span class="h2">Primary sampling units (PSU)</span>
<br />These are units of area with identifiable boundaries on the ground, which group a set of homes, whose conformation criteria depend on each project.</p>
<p>To construct the primary sampling units, geographical elements were used that result from primary units that vary the least over time and are more identifiable in the field, as is the case of locales, blocks and BGSA (Basic Geo-Statistical Areas).</p>
<p>In a first stage, the primary sampling units that make up the sampling elements were selected. In the case of locales with blocks and segments in scattered rural areas, homes are selected in a second stage.</p>
<p>PSUs were covered in their entirety and the lists of homes were drawn up, which is why they are also known as the listing area, a term that will be used synonymously with PSU. The criteria for their conformation depend on the size of the locale to which they belong:</p>
<div class="i1">- In metropolitan areas, locales with 100,000 or more residents and state capitals. Each PSU has a minimum of 80 inhabited homes, optimally 100, and a maximum of 160. They are made up of one or more contiguous blocks belonging to one or more BGSA.<br />- In a city extension. Each PSU shall have a minimum of 160 inhabited homes, a maximum of 300 and optimally 200. PSUs, like those mentioned in the preceding paragraph, are made up of one or more contiguous blocks belonging to one or more BGSA.<br />- In the rural area. These are a set of bordering locales grouping a total of between 160 and 300 homes, optimally 200.</div><p>PSUs may be part of a BGSA, a complete BGSA or two or more joined BGSAs.
