Power Analysis Surge

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!

Coin Chops: Can the Law of Averages be Replaced by the Law of Probability?

Alas, to the ‘average’ consumer of statistics, unlike we statisticians and data analysts, Probability is a sort of Comic I mean Cosmic Force i.e. ‘The Laws of Probability’ . David Hand OBE FBA has entertainingly looked at misunderstandings of this Comic Force and Coincidences in ‘the improbability principle: why coincidences, miracles and rare events happen all the time’ (2014).

But sitting here in the State Library of Victoria, I’m reading Frank ‘Power Without Glory’ Hardy’s novel ‘Four-legged lottery’ (1958). On page 179 of the Gold Star paperback edition there’s a bit of blarney about the ‘law of probability’ replacing the ‘law of averages’ where one of the two main characters, a professional gambler by the name of Jim Roberts, talks about the Anglo-Australian game of Two-Up which involves throws of pairs of coins, and is legal in Australian casino’s and traditionally, on the streets on ANZAC Day (25th April)..

‘in an honestly conducted two-up school, an equal number of heads and tails will be thrown over a long period; both head and tail bettor must lose [as the ‘house’ must take a percentage]. [To try and overcome the Law of Averages, giggle!] a tail better can back the tail on every spin – only for two throws, doubling [the] stake on the second throw if the spinner [bets heads] the first time. In this way [he or she] defeats the law of average <by winning> every time a spinner throws [both tails or one head and one tail and only loses when spinner throws both heads]’. Time for a simulation !

Watch this space. Same Stat Time! Same Stat Channel!