At the end he gives two ways running Monte Carlo simulations, spreadsheet plugins, and his own app Casual. Surely there are more. Are there other tools for Monte Carlo sims that HN'ers use and like? Preferably local FOSS apps?
You can do a monte carlo simulation in a spreadsheet without a plugin, too. For each of the inputs, create a column where the cell retrieves a random value according to the probability distribution you pick. Then, drag down 1000 rows or 10000 rows or whatever, and finally calculate percentiles based off of the outputs of each row.
A few years ago when I met my now-wife, I was paying a mortgage and she was paying rent, and we wanted to get an idea of what we could afford if we wanted to stick with the budget were were already comfortable with. So the inputs were the possible sale price of my house, the possible interest rate of the new mortgage, etc. We experienced what the article describes; while we were quite conservative about each of all of those elements, the 99th percentile was a lot less conservative than the worst-case scenario of each and every input we plugged in, and it gave us an accurate target of what kind of home price we felt we could actually afford.
I use the @Risk tool he references, its handy because its easy to spit out tables that upper management can sagely nod their heads to and ask what you're doing about the top 2 drivers of uncertainty. that and those with finance backgrounds are also familiar with the tool and like to see it.
