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Canada's 'Random' Immigration Lottery Uses Microsoft Excel, Which Isn't Actually Random (gizmodo.com)
An anonymous reader writes: Last year, Canada introduced a new lottery system used to extend permanent-resident status to the parents and grandparents of Canadian citizens. The process was designed to randomly select applicants in order to make the process fairer than the old first-come, first-served system. There's just one problem: the software used to run the lottery isn't actually random. The Globe and Mail reported the Immigration, Refugees and Citizenship Canada (IRCC) uses Microsoft Excel to run the immigration lottery to select 10,000 people for permanent resident status from a field of about 100,000 applications received each year. Experts warned that the random number generating function in Excel isn't actually random and may put some applicants at a disadvantage.
First, it's best to understand just how the lottery system works. An Access to Information request filed by The Globe and Mail shows that IRCC inputs the application number for every person entering the lottery into Excel, then assigns them a random number to each using a variation of the program's RAND command. They then sort the list from smallest to largest based on the random number assigned and take the first 10,000 applications with the lowest numbers. The system puts a lot of faith in Excel's random function, which it might not deserve. According to Universite de Montreal computer science professor Pierre L'Ecuyer, Excel is "very bad" at generating random numbers because it relies on an old generator that is out of date. He also warned that Excel doesn't pass statistical tests and is less random than it appears, which means some people in the lottery may actually have a lower chance of being selected than others.
First, it's best to understand just how the lottery system works. An Access to Information request filed by The Globe and Mail shows that IRCC inputs the application number for every person entering the lottery into Excel, then assigns them a random number to each using a variation of the program's RAND command. They then sort the list from smallest to largest based on the random number assigned and take the first 10,000 applications with the lowest numbers. The system puts a lot of faith in Excel's random function, which it might not deserve. According to Universite de Montreal computer science professor Pierre L'Ecuyer, Excel is "very bad" at generating random numbers because it relies on an old generator that is out of date. He also warned that Excel doesn't pass statistical tests and is less random than it appears, which means some people in the lottery may actually have a lower chance of being selected than others.
Quoting the original article: http://www.pages.drexel.edu/~bdm25/excel2007.pdf
The random number generator has always been inadequate. With Excel 2003, Microsoft attempted to implement the Wichmann–Hill generator and failed to implement it correctly. The fixed version appears in Excel 2007 but this fix was done incorrectly. Microsoft has twice failed to implement correctly the dozen lines of code that constitute the Wichmann–Hill generator; this is something that any undergraduate computer science major should be able to do. The Excel random number generator does not fulfill the basic requirements for a random number generator to be used for scientific purposes:
it is not known to pass standard randomness tests, e.g., L’Ecuyer and Simard’s (2007) CRUSH tests (these supersede Marsaglia’s (1996) DIEHARD tests—see Altman et al. (2004) for a comparison);
it is not known to produce numbers that are approximately independent in a moderate number of dimensions;
it has an unknown period length; and
it is not reproducible.