Performs unconditional exact tests and power calculations for 2x2 contingency tables. Calculates Barnard's test (1945) <doi:10.1038/156177a0> using the original CSM test (Barnard, 1947 <doi:10.1093/biomet/34.1-2.123>), using Fisher's p-value referred to as Boschloo's test (1970) <doi:10.1111/j.1467-9574.1970.tb00104.x>, or using a Z-statistic (Suissa and Shuster, 1985, <doi:10.2307/2981892>). Calculations confidence intervals for the difference in proportion.