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Identify the experimental units or subjects, the explanatory variables (factors), the treatments, and the response variables. How can we reduce the rate of refusals in telephone surveys? Most people who answer at all listen to the interviewer鈥檚 introductory remarks and then decide whether to continue. One study made telephone calls to randomly selected households to ask opinions about the next election. In some calls, the interviewer gave her name, in others she identified the university she was representing, and in still others she identified both herself and the university. For each type of call, the interviewer either did or did not offer to send a copy of the final survey results to the person interviewed. Do these differences in the introduction affect whether the interview is completed?

Step by step solution

01

Identifying the Experimental Units or Subjects

The experimental units or subjects in this study are the individuals in the randomly selected households who receive the telephone call. These are the people to whom the treatments are applied and whose responses are being measured in terms of whether they complete the interview.

02

Identifying the Explanatory Variables (Factors)

The explanatory variables or factors in this study are elements of the telephone introduction. Specifically, they include (1) whether the interviewer gives her name, (2) whether she mentions the university she represents, and (3) whether she offers to send the final survey results. These variables are manipulated to observe their impact on the response variable.

03

Describing the Treatments

Treatments in this context are the different combinations of factors applied during the telephone introduction. These combinations include: 1) interviewer only gives her name, 2) interviewer only mentions the university, 3) interviewer gives both her name and university, and 4) whether or not an offer to send results is made. These combinations are applied to understand their effect on the response.

04

Identifying the Response Variables

The response variable in this study is whether the telephone interview is completed or refused by the individual. It is the outcome being measured to evaluate the effect of varying introductory strategies.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Explanatory Variables

In the context of experimental design, explanatory variables, also known as factors, are the elements that researchers manipulate to observe how they affect the response variable. In the telephone survey study, the explanatory variables are linked to the introduction style used by the interviewer. These variables include:

• Whether the interviewer gives her name.
• If the university she represents is mentioned.
• Whether she offers to send the final survey results.

These variables are the key components that the researchers change intentionally to understand their impact on the responses, which in this case, is whether the interview is completed.

Response Variables

The response variable is the main focus of the study; it is what the researchers are interested in observing and measuring. For this exercise, the response variable is straightforward: it is whether the telephone interview is completed or refused. This outcome is crucial because it will help the researchers determine which introductory strategies in telephone calls are most effective in reducing refusals. By analyzing the response variable, researchers can draw conclusions about the real-world effectiveness of different intro strategies.

Experimental Units

Experimental units or subjects are the individuals or items that are observed and measured in a study. They are the ones to whom the treatments are applied, and their responses are recorded. In the context of this experiment, the experimental units are the individuals from the randomly selected households who receive a phone call. These people are the subject of the study, as the primary goal is to observe how various introductory strategies affect their decision to participate or not in the survey. Selecting a random sample ensures that the results are generalizable to a broader population.

Treatments

Treatments refer to the specific conditions applied to experimental units, laid out by the combinations of the explanatory variables. During the telephone survey, the treatments are the different introductions used by the interviewer. The researcher considered four possible combinations:

• The interviewer gives only her name.
• The interviewer mentions only the university.
• The interviewer gives both her name and the university.
• Each of these might also include the optional offer of sending survey results.

Each of these combinations serves as a unique treatment. By comparing the effectiveness of these treatments, researchers can identify which introduction strategy best reduces refusal rates in telephone surveys.