Who gives a toss: the statistics of coins

Spring is here in Melbourne, and a time for fashionable horse racing, including The Melbourne Cup in November., once attended by Mark Twain. Australia is also home of the “two-up” coin tossing game (descended from the British pitch and toss), played in outback pubs, hidden city lanes and now Australian casino’s, described in great old Australian novels such as Come In Spinner, and the eerie book and 1971 movie Wake in Fright (aka Outback).

In the 18th century, the Comte de Buffon obtained 2048 heads from 4040 tosses, while more recently and not to be outdone the statistician Karl Pearson obtained 12,012 heads out of 24,000 tosses (The Jungles of Randomness by Ivars Peterson, 1998). Of course a misunderstanding of the law of large numbers or so-called law of averages, makes the uninitiated think that if there’s say seven heads in a row, a cosmic force will decide “hang on that coin is coming up heads more than 50%, better make the next one a tail”).

While it doesn’t look at two-up, “Digital Dice” by the always entertaining Paul Nahin (2008) examines a tricky coin-tossing problem posed in 1941 and not solved until 1966. Prof Paul shows how to solve it using a computer-based Monte Carlo method, itself named after that famous casino in Monaco, where James Bond correctly observed that “the cards have no memory”.

And who says stats isn’t relevant?!

Electric Stats: PSPP and SPSS

Most people use computer stats packages if they want to perform statistical or data analysis. One of the most popular packages, particularly in psychology and physiotherapy, is SPSS, now known as IBM SPSS. Although there is room for growth in some areas such as ‘robust regression’ (regression for handling data that may not follow the usual assumptions), IBM SPSS has many jazzy features / options such as decision trees and neural nets and Monte Carlo simulation, as well as all the old faves like ANOVA, t-tests and chi-square.

I love SPSS and have been using it since 1981, back when SPSS analyses had to be submitted to run after 11 pm (23:00) so as not to hog the ‘mainframe’ computer resources. Alas, as with Minitab, SAS and Stata and others, SPSS can be expensive if you’re not a student or academic. An open source alternative that is free as in sarsparilla and free as in speech, is GNU PSPP, which has nothing whatsoever to do with IBM or the former SPSS Inc.

PSPP has a syntax or command line / program interface for old school users such as myself, *and* a snazzy GUI or Graphic User Interface. Currently, it doesn’t have all the features that 1981 SPSS had (e.g. ‘two-way ANOVA’), let alone the more recent features, although it does have logistic regression for binary outcomes such as depressed / non depressed. PSPP is easy to use (easier than open source R and perhaps even R Commander, although nowhere near as powerful).

PSPP can handle most basic analyses, and is great for starters and those using a computer at a worksite etc where SPSS is not installed, but need to run basic analyses or test syntax. The PSPP team is to be congratulated!

http://www.gnu.org/software/pspp/   free, open-source PSPP

http://www-01.ibm.com/software/analytics/spss/  IBM SPSS

(students and academics can obtain less expensive versions of IBM SPSS from http://onthehub.com)