A psychologist is interested in how well clients are doing on a certain treatment. The data collected from a client’s survey response will create what type of scale?

The correct response is that the data collected from a client’s survey response will create an interval scale. An interval scale is a quantitative measurement scale where the distance between each value is equal, allowing for meaningful comparisons of the degree of differences between measurements. In a psychological context, survey responses often use Likert-type scales (e.g., 1 to 5 or 1 to 7) that capture the intensity of feelings or opinions. Each point on the scale represents equal intervals in terms of the underlying construct being measured, like satisfaction or symptom severity.

The interval nature of the scale means that while it is possible to say that one score is greater than another and that the difference between scores is meaningful, it does not include a true zero point that represents the absence of the measured attribute. This characteristic distinguishes it from a ratio scale, where a true zero is present, allowing for statements about ratios to be made (e.g., twice as much).

In contrast to summary, ordinal, or ratio scales, the interval scale provides the nuanced ability to measure differences related to psychological states effectively, making it well-suited for treatment evaluations in psychology.