Calculate the minimum sample size for a Pilot SMART

About This Applet

This code is used to estimate and compare the mean of a continuous end-of-study outcome for the adaptive interventions embedded in a SMART.

How can a behavioral scientist use this applet?

Behavioral intervention scientists can use this code to select the sample size for a Pilot SMART in preparation for a subsequent full-scale SMART. The typical primary aims in a Pilot SMART are to (i) examine the feasibility and acceptability of the embedded adaptive interventions proposed for a full-scale SMART (both from the perspective of the clinicians providing interventions and the patients being treated); and (ii) to prepare the research team to conduct a successful full-scale SMART. To use the applet, a behavioral intervention scientist will input the minimum number of participants they would like assigned to all treatment sequences to achieve these aims, and the applet will return the minimum, total sample size to recruit for the Pilot SMART.

What method does this applet implement?

This code calculates the minimum total sample size N needed to ensure that with a fixed fixed probability k, at least m participants will fall into each of the treatment sequences in a Pilot SMART. The user will input k and m, and the web applet will output N. The two sources of randomness are the randomized treatment assignments at each stage, and the response/non-response rate at the end of stage 1.

Related References

1. Kim, H., Ionides, E., & Almirall, D. (2016). A sample size calculator for SMART pilot studies. SIAM undergraduate research online, 9, 229.

2. Almirall, D., Compton, S. N., Gunlicks‐Stoessel, M., Duan, N., & Murphy, S. A. (2012). Designing a pilot sequential multiple assignment randomized trial for developing an adaptive treatment strategy. Statistics in medicine, 31(17), 1887-1902.