December-February (and generally March) is Summer in the Southern Hemisphere. It can get pretty hot even in the more temperate southern states (= northern states in the Northern Hemisphere). Today, the last day of 2015, has an expected top of 40 Celsius, which is 104 Fahrenheit and a nose-peeling 313.5 Kelvin!
Summer is also the start of the Australian Academic Year, and Grant Season, where everyone is looking for Statisticians (who are in swimming pools or pool halls) to run power analyses for them. With no statisticians to be found, it’s off to the library and borrow whatever randoms they can find, or use one of the free web packages, which often works out like a home haircut.
There’s great specific software such as PASS http://www.ncss.com and NQuery Adviser & Nterim http://www.statsols.com/products/nquery-advisor-nterim/
They’re not cheap (but neither are grants!), and aid professional statisticians as well. There’s R of course, and the excellent menu-driven power and sample size routines in SAS and Stata.
But first define the differences you’re expecting, based on the actual Literature as well as Clinical Judgement, and always see a Statistician!