Publications by dan
On not going viral
LACK OF EVIDENCE FOUND FOR THINGS “GOING VIRAL” ON MAJOR WEB PLATFORMS This week the reader is directed to Messy Matters to read up on research conducted by Sharad Goel, Duncan Watts and Dan Goldstein in which they hunted for traces of “viral” diffusion on six web platforms including Twitter, Facebook, and Yahoo!. The results run counter...
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How many NYC restaurants get As on their health inspections?
WITH DATA LIKE THESE, WHO CAN SAY? Decision Science News is no stranger to misleading infographics in free New York newspapers. We could upgrade to real newspapers, but we find that playing “spot the infographic flaw” really makes the time fly on the subway. We saw the above graphic in a paper called Metro. In New York City, restaurants are ...
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Dollars and cents: How are you at estimating the total bill?
ROUNDING HEURISTICS AND THE DISTRIBUTION OF CENTS FROM 32 MILLION PURCHASES When estimating the cost of a bunch of purchases, a useful heuristic is rounding each item to the nearest dollar. (In fact, on US income tax returns, one is allowed to round and not report the cents). If prices were uniformly distributed, the following two heuristics wou...
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Do cents follow Benford’s Law?
MANY THINGS FOLLOW BENFORD’S LAW. CENTS DON’T. A commenter on our last post brought up Benford’s law, the idea that naturally occurring numbers follow a predictable pattern. Does Benford’s law apply to the cent amounts taken from our 32 million grocery store prices? Benford’s law, if you don’t know about it, is an amazing thing. If y...
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Keep your files in sync for free
COSTLESS FILE SYNCHRONIZATION TECHNIQUES IN INCREASING ORDER OF COMPLEXITY It is not uncommon to have two computers at work, four at home, and a server out on the wide open internet. How to keep all these files in sync? Here are some file synchronization tools that we use, listed in increasing order of complexity. Dropbox dropbox.com Setup: Eas...
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You’ve got the whole world in your portfolio
LEARN HOW TO IMPORT WORLD BANK DATA AND INVEST IN THE WHOLE WORLD Click to enlarge The market cap of the countries comprising 90% of the world’s market cap (end 2010) A famous finance professor once told us that good diversification meant holding everything in the world. Fine, but in what proportion? Suppose you could invest in every country ...
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Some code to help you remember numbers
HANDY COMPUTER PROGRAMS FOR TURNING NUMBERS INTO MEMORABLE WORDS Two posts ago we showed you the digit sound system for remembering numbers. This week we provide two Python programs (and one R program) to help you create mnemonics. w2num.py – converts every word in the English language to a number find.py – takes a longish number and gives y...
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How to square numbers in your head
MENTALLY MULTIPLY NUMBERS BY THEMSELVES Babbage’s Difference Engine is fueled by squares Even in the age of ubiquitous computing, its usually faster to do a simple operation like squaring a number in your head as opposed to doing it on paper or firing up R. Everyday decision making in science needs to happen in a fast and frugal manner. Assumi...
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Time-based internet advertising
USING TIME, IN ADDITION TO IMPRESSIONS, FOR INTERNET ADVERTISING From Goldstein, Suri, McAfee (2011) Last week it was announced that Facebook is rotating its ads after a certain time of exposure. In 2011 and 2012, Sid Suri, Preston McAfee, and Dan Goldstein published a couple papers putting forth and improving the idea of time-based internet ad...
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The housing bubble: Where are we?
DIFFERENT CITIES TELL DIFFERENT STORIES Last spring we looked at the state of the housing bubble in the US. The question on readers’ minds then was “where is it going next”? Since Decision Science News is looking for a place to buy, it is on our minds as well. It’s been more than a year, so let’s have a look. Above, we see the plot for...
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