Design and Analysis of 2x2 Factorial Trial

Used for the design and analysis of a 2x2 factorial trial for a time-to-event endpoint. Performs power calculations and significance testing. Important reference papers include Slud EV. (1994) < https://www.ncbi.nlm.nih.gov/pubmed/8086609> Lin DY, Gong J, Gallo P, Bunn PH, Couper D. (2016) Leifer ES, Troendle JF, Kolecki A, Follmann DA. (2019) < https://github.com/EricSLeifer/factorial2x2/blob/master/Leifer%20et%20al%20Factorial.pdf>.