Some observers worry that this year’s census carries the same potential for mayhem as last month’s Iowa caucuses, except on an infinitely larger scale. Both events involve a large population, new technology that has not been thoroughly tested and an entire country waiting on the results. This is the first once-a-decade census in which most people are being encouraged to answer questions via the internet. Census workers who knock on doors of homes will use smartphones and a new mobile app to relay answers. Some watchdog agencies and lawmakers are concerned about whether the systems are ready for prime time.