False: |Republicans| + |Democrats| = |Voters|. Pragmatically, the missing set: {Voters}/{Republicans}U{Democrats} usually gets dropped somehow, and when it does, elections are won or lost. Another example is |Voters| + |Nonvoters| = |Population| This is what I would call poor-logic, and it's easy to break. What about the disenfranchised? Clearly {Nonvoters} includes {Disenfranchised-T}, but {Voters} does not include {Disenfranchised-F}! Again, elections can be won or lost on this logic. None of this is ever said by politicians, but as far as I can see, it's implicit to what they are doing, especially with United States of America, right now. --Brad On Fri, Sep 4, 2020 at 9:55 AM James Propp <jamespropp@gmail.com> wrote:

Does anyone know of any widely-promulgated bogus assertions of the form “The cardinality of set A plus the cardinality of set B equals the cardinality of set C” (where the C is something like the union of A and B) that sounds convincing until you step back and realize either (a) there are elements of C that are elements of neither A nor B, or (b) there are elements of C that are elements of both A and B?

Here I’m talking about flimflam at the interface between math and culture (not mistakes made by mathematicians in a mathematical context); e.g., fallacious stuff said by public figures.

Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun

"If you're not for us, you're against us." How many people are backing candidates in 2016: https://www.statisticshowto.com/wp-content/uploads/2014/01/pie-chart-mislead... Lots of other examples at that site: https://www.statisticshowto.com/misleading-graphs/ This whole subreddit: https://www.reddit.com/r/badstats/ GDP calculations have to be careful about double counting. PCR tests for covid have a roughly 5% false positive rate and (after showing symptoms) a roughly 38% false negative rate https://www.sciencedaily.com/releases/2020/06/200610094112.htm https://www.health.harvard.edu/blog/which-test-is-best-for-covid-19-20200810...). On Fri, Sep 4, 2020 at 8:55 AM James Propp <jamespropp@gmail.com> wrote:

Does anyone know of any widely-promulgated bogus assertions of the form “The cardinality of set A plus the cardinality of set B equals the cardinality of set C” (where the C is something like the union of A and B) that sounds convincing until you step back and realize either (a) there are elements of C that are elements of neither A nor B, or (b) there are elements of C that are elements of both A and B?

Here I’m talking about flimflam at the interface between math and culture (not mistakes made by mathematicians in a mathematical context); e.g., fallacious stuff said by public figures.

Jim Propp _______________________________________________ math-fun mailing list math-fun@mailman.xmission.com https://mailman.xmission.com/cgi-bin/mailman/listinfo/math-fun

-- Mike Stay - metaweta@gmail.com http://math.ucr.edu/~mike https://reperiendi.wordpress.com