किस प्रकार के प्रतिचयन (sampling) में शोधकर्ता उन व्यक्तियों की एक छोटी संख्या की पहचान करते हैं जिनमें लक्षित विशेषताएं होती हैं, और फिर उनका उपयोग उन अन्य लोगों की पहचान करने और उनसे संपर्क करने के लिए करते हैं जो अध्ययन में शामिल होने के योग्य हैं?

Given below are two statements: one is labeled as Assertion (A) and the other is labeled as Reason (R). Assertion (A): Though ex-post facto research examines cause and effect relationships, it is not part of experimental research. Reason (R): In ex-post facto research, the effect or change in the independent variable has already occurred and cannot be manipulated. In the light of the above statements, choose the most appropriate answer from the options given below:

Given below are two statements: one is labeled as Assertion (A) and the other is labeled as Reason (R). Assertion (A): In non-probability sampling, the units are selected at the discretion of the researcher. Reason (R): Non-probability samples do not require a sampling frame. In the light of the above statements, choose the most appropriate answer from the options given below: