Let's pretend your mum was opening a diner, and she wants to sell the best fries in town. She has a good recipe, but knows with a little tweaking, it could be great.<p>She has a few regulars who come for lunch each day, so decides to see what they think of little changes she makes.<p>She starts by adjusting the amount of salt, a little more for some tables, a little less for others. She notices sometimes tables order more refills of their bowl of fries, and even stay longer (buying drinks, etc...).<p>Rather than making bigger changes and directly asking customers their preference ("do you prefer our new super-fries or our classic-fries?"), she's decided to focus on more subtle (often not very noticeable) changes, and most importantly, watched the reactions or changes in behavior to influence any longer term changes.<p>(imagine everyone she asked said they like some new seasoning, but now only order a single, small serving. maybe the original is actually preferred?)