treatment: vector. treatment assignment for patients, 1 for treatment group and 0 for control group
outcome: vector. normal outcome of the trial.
complete: vector. similar length as treatment and outcome variable, 1 for complete outcome, 0 for loss to follow up. If complete is not provided, the dataset is assumed to be complete.
.data: NULL. stores the normal data for analysis, please do not fill it in.
Returns
a list with treatment, outcome and loss to follow up vector with normal outcome.