Hi all
What could be the process of estimating sample size for a cognitive test being developed? The test is not an adaptation of any existing test and has to be used for patients with schizophrenia. In the first stage, I understand that a healthy participant group will be required to have the normative data followed by administration on the clinical group. Hence, what could be the process of estimating the sample size of the healthy control and the clinical groups?
The size of the sample for developing a new measurement instrument is not necessarily the same as for testing its predictive ability relative to a control group.
For the development of the instrument, you will typically need to do Confirmatory Factory Analysis, and a classic recommendation there is that the number of observation should be 10 times the number of items in your scale.
Once you have a testable version of the scale, you can assess the sample size for a comparison to a control group using he program g*Power to determine the power of your text.
I'm not sure if I'm understanding this correctly. Do you want to pre-test the measuring tools? The primary purpose of the pretest is to verify that the target audience understands the questions and response options of the test tool. A cognitive interview is usually used to understand the cognitive level of the subjects on the measurement content, scheme, or tool. If necessary, the measurement tool entry can also be revised appropriately based on the results to ensure the feasibility of this tool in patients with schizophrenia.
The following literature can be used as a reference for sample size estimation in pre-testing.
Perneger, T. V., Courvoisier, D. S., Hudelson, P. M., & Gayet-Ageron, A. (2015). Sample size for pre-tests of questionnaires. Quality of life research : an international journal of quality of life aspects of treatment, care and rehabilitation, 24(1), 147–151. https://doi.org/10.1007/s11136-014-0752-2
I think it is difficult to draw a strong distinction between pilot testing and pretesting, but in general pilot testing precedes pretesting, and its primary goal is to ensure that the items mean the same thing to the participants and the researchers. Cognitive interviewing is a classic form of pilot testing.
In contrast, pretesting asks whether the instrument performs as intended. Classic indicators in pre-testing include coefficient alpha and factor analysis.
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