Please accept my apology for harshness of tone.Well, I'm not so sure the numbers do speak for themselves. If they did, we wouldn't have people panicking at normal common cause variations.
You're right that selling cars isn't a directly controllable process. However, like any process its stability can be tracked using common statistical methods. Why bother? Because folks here are getting in more of a sweat about short-term swings in reservation numbers than they need to.
I picked on the 6-point example not because it is the only indicator of a trend, but because it's one that people who don't do statistical process control can grasp. You are correct, that there are many charting methods -- most of which I'm rusty on, not having used them in 15 years or so. But if people can get it that apparent swings in sales per unit of time may not be telling any story at all, that's important and helpful to folks who are desperate for Elio to succeed and doubtful that it will.
It's like trying to track the stock market daily, and make buying decisions on that basis. Good way to lose your shirt. So with Elio reservation numbers -- the total number is, of course increasing, but the RATE of increase can vary ... without necessarily meaning the company is floundering or triumphing.
I do think your comments about my knowledge of SPC (or lack thereof) were inappropriately harsh. At least I went through a Deming 3-day ... did you?