This package provides a sample size calculator for Micro-randomized Trials with binary outcomes. The sample size formula is developed in “Sample Size Considerations for Micro-Randomized Trials with Binary Outcome” by E. Cohn, T. Qian, and S. Murphy. This is currently a work in progress; contact Tianchen Qian (qiantianchen.thu@gmail.com) if you would like a copy of the draft manuscript.

Before using the calculator the user should have knowledge of the following:

**Study Setup**The number of decision time points and the randomization probability, i.e. the probability of assigning the treatment at each decision time point.**Availability**Treatment can only be provided when an individual is available. The expected availability is the probability a person is available to receive the intervention at the decision times. You need to select a time-varying pattern for the expected availability.**Success Probability Null Curve**The Success Probability Null Curve at each decision time point is defined as the probability of the proximal outcome equal to 1 for available individuals who are not assigned treatment. You need to provide the trend of success probability null curve.**Proximal Treatment Effect**The Proximal Treatment Effect at each decision time point is defined as the mean difference in the proximal outcome between available people who are assigned a treatment versus available people who are not assigned treatment. In this work, we only consider the binary treatment. You need to provide the trend of proximal treatment effects.

The outputs one can get using this package are mainly two values, power and sample size. In both cases, you will need to input the desired significance level.