Sample Size Calculations in Clinical Research


The PICOT question for this study is “In children with asthma between the ages of 5 and 19 (P), does a combination program consisting 5 weeks of education sessions, once per week including children and their families in the primary care setting and a daily controller medication (I) compared to using controller medication and one education section (C) reduce asthma exacerbations (O) over a one-year period (T)?” Here, the plan involves a year-long study of children’s health-related outcomes in two groups – one part of participants receives one educational lesson and controller medication daily.

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The other group adheres to the new program and goes through 5 weeks of training sessions, as children with asthma and their caregivers visit a weekly lesson apart from taking medication. Here, the use of a group-randomized longitudinal design is required.

Determining Sample Size

In order to establish how many children should participate in the study, one can rely on scholarly literature. For example, Kintner et al. (2015) conducted a similar study where they implemented a new way of educating children and adolescents with asthma. They invited 270 caregivers of children and 216 of them responded and underwent the training program (Kintner et al., 2015). The authors, however, note that the sample was limited with time, and a total of 205 persons finished their education.

As a model of a group-randomized trial is proposed, the research requires two groups of people where the involved members will complete two different studying programs. In this case, the intraclass correlation (ICC) and cost per person should be determined (Chow, Shao, Wang, & Lokhnygina, 2017). One can suggest calculating these measures in order to lower the width of the confidence interval – the number of 250 to 200 participants seems sufficient for the study.

Pre-Test Evaluation

A baseline pretest should include the number of participants and the measures that will be influenced and recorded during the study’s progression. For example, the authors should include data pertaining to the new and old training programs such as the caregivers’ knowledge about health promotion, hygiene, exercising guidelines, or sleeping schedule. To complete the evaluation, all participants receive a questionnaire where they answer questions provided above as well as inquiries related to exacerbations. The responses are measured using a scale from 1 to 5, one being “never” to 5 being “always.”

Then, mean scores are calculated with the range of 1.00 to 5.00, and Cronbach’s standardized alpha correlation is added to review the data and locate major issues (Kintner et al., 2015). As a result, the gathered information should provide the study with a measurable foundation.


The intervention should be implemented and recorded through multiple tests during the program’s active phases. Caregivers participating in the trial should answer questions about their children’s health and their knowledge about asthma. Moreover, children’s number of exacerbations can be self-recorded or monitored by a healthcare facility. Such points in the initiative as one month and 12 months after the start of the trial are sufficient to record changes. During this time, families enrolled in the program undergo checks that review the child’s exacerbations and compare the outcomes of the two groups to each other.

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Post-Test Evaluation

The post-test evaluation should include the same calculations that are provided in the pretest phase. Caregivers should answer some questions about children’s health and education. Moreover, the initial numbers of exacerbations should also be considered, and the results should be appraised with coefficient and variance change. Fitted values can indicate the increase or decrease in exacerbation rates between the two clusters – participants who underwent a new and old training program.


Chow, S. C., Shao, J., Wang, H., & Lokhnygina, Y. (2017). Sample size calculations in clinical research (3rd ed.). Boca Raton, FL: CRC Press.

Kintner, E. K., Cook, G., Marti, C. N., Allen, A., Stoddard, D., Harmon, P.,… Van Egeren, L. A. (2015). Effectiveness of a school‐and community‐based academic asthma health education program on use of effective asthma self‐care behaviors in older school‐age students. Journal for Specialists in Pediatric Nursing, 20(1), 62-75.

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