MENTALLY MULTIPLY NUMBERS BY THEMSELVES Assume you know your multiplication tables up to 10x10. Here's how to compute the squares of numbers from 11 to 100.
Blog Archives
Some code to help you remember numbers
Two posts ago we showed you the digit sound system for remembering numbers. This week we provide two computer programs to help you create mnemonics.
You’ve got the whole world in your portfolio
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 in the world. How much would you invest in each? In a market-capitalization weighted index, you'd invest in each country in proportion to the market value of its investments (its "market capitalization")....
Keep your files in sync for free
It is not uncommon to have two computers at work, four at home and a server out on the wild, wild internet (that's what we have, anyway ... wait, we forgot one in London). How to keep all these files in sync? Here are our file synchronization tips.
Do cents follow Benford’s Law?
Benford's law is an amazing thing. If you know the probability distribution that classes of "natural" numbers should have, you can detect where people might be faking data: phony tax returns, bogus scientific studies, etc.
Dollars and cents: How are you at estimating the total bill?
When estimating the cost of a bunch of purchases, a useful heuristic is rounding to the nearest dollar. (In fact, on US income tax returns, one is allowed to omit the cents). If prices were uniformly distributed, the following two heuristics would be equally accurate: * Rounding each item up or down to the nearest dollar and summing * Rounding each...
How many NYC restaurants get As on their health inspections?
Decision Science News is no stranger to misleading infographics in free New York newspapers. We could stop reading them entirely, but we find that playing "spot the infographic flaw" makes time fly on the subway. Recently we saw the above graphic in a paper called Metro. Can you spot the goof?
On not going viral
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 Twitter, Facebook, Yahoo!, and beyond. The results run counter to mainstream intuition.
The housing bubble by city
The housing bubble by city. Miami sailed high and fell far. Detroit rose modestly and but dropped more than it went up. Dallas held steady. DC is enjoying a bit of renewed growth, but are in and New York yet to fall?
Zero Inflated Models and Generalized Linear Mixed Models with R.
Zuur, Saveliev, Ieno (2012).
