In my experience, providing effective estimates with actual data requires: - know enough about what you are doing to estimate at all - screening for clients w

In my experience, providing effective estimates with actual data requires: - know enough about what you are doing to estimate at all - screening for clients who will make it possible to work effectively, and knowing how to do that -setting realistic expectations about what can actually be accomplished - the client has the resources to pay for the project, including multiple iterations of dealing with the unexpected - you the resources to make efficient use of the clients resources - you don't promise to deliver something that you quoted at a higher price when the client talks you down to a lower price