If the lognormal distribution is correct, the 95% confidence interval is a bit over 5 times the developer's gut-feeling estimate. The 99% confidence interval is

If the lognormal distribution is correct, the 95% confidence interval is a bit over 5 times the developer's gut-feeling estimate. The 99% confidence interval is 10 times the developer's gut-feel estimate. We found a lot of data to back this up, but your mileage may vary.