"Why do Fermi estimates work? [...] multiplying estimates corresponds to adding their logarithms; thus one obtains a sort of Wiener process or random walk on the logarithmic scale, which diffuses as sqrt{n}. More precisely, if one makes a Fermi estimate of ''n'' steps, with standard error sigma units on the log scale, then the overall estimate will have standard error sqrt{n}*sigma, since the standard deviation of a sum scales as sqrt{n} in the number of summands."

## disconcision

## andrew blinn

"Why do Fermi estimates work? [...] multiplying estimates corresponds to adding their logarithms; thus one obtains a sort of Wiener process or random walk on the logarithmic scale, which diffuses as sqrt{n}. More precisely, if one makes a Fermi estimate of ''n'' steps, with standard error sigma units on the log scale, then the overall estimate will have standard error sqrt{n}*sigma, since the standard deviation of a sum scales as sqrt{n} in the number of summands."