Gigo’s law of deduction: Garbage in, garbage out.
One of my jobs is to assist students in analyzing their data. Given it’s media and computer science students with an truly excellent course in statistics (yeah, I do that course as well), but the students do the work a few semesters later, there is a huge variance in how organized and capable these students are.
So I did a short two-pager about things to remember for data analysis — when they ask others for help, that is. I think it’s useful, so you find the German and a quick and dirty English translation here.
And actually, data analysis is fun (mostly, unless the numbers break your heart). But you need to understand what is in front of you. Otherwise you can calculate some amazingly stupid things.