I was chatting with my Dad last night and the topic of calculators came up. My Dad, a Biology Professor for many years, had strong feelings about these magical little devices and how they impacted his students. The problem, he explained, is that the calculator always gives you an answer. And because the answer is on a calculator (or in an Excel Spreadsheet, or part of a Matlab Prompt session, or echo'd next to an R prompt) it has the bias of appearing as truth. The result: his students would blindly hand in answers that with even a little thought showed them to be ridiculous.
So what's the solution, I pressed back?
Simple, he explained: before you starting using the calculator figure out a guess as to what you believe the solution should be.
If the solution and your guess match, awesome!
If the solution and your guess don't match, that's just as important: why not? Was an assumption of yours off? Or, did you merely type in an extra zero when keying in your inputs?
Solid advice Dad, and one I'll be using from now on.