The Goal

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assemble the product. The product has to be assembled before we can ship it. And so on.

But you find dependent events in any process, and not just those in a factory. Driving a car requires a sequence of dependent events. So does the hike we're taking now. In order to arrive at Devil's Gulch, a trail has to be walked. Up front, Ron has to walk the trail before Davey can walk it. Davey has to walk the trail before Herbie can walk it. In order for me to walk the trail, the boy in front of me has to walk it first. It's a simple case of depen- dent events.

And statistical fluctuations?

I look up and notice that the boy in front of me is going a little faster than I have been. He's a few feet farther ahead of me than he was a minute ago. So I take some bigger steps to catch up. Then, for a second, I'm too close to him, so I slow down.

There: if I'd been measuring my stride, I would have re- corded statistical fluctuations. But, again, what's the big deal?

If I say that I'm walking at the rate of "two miles per hour," I don't mean I'm walking exactly at a constant rate of two miles per hour every instant. Sometimes I'll be going 2.5 miles per hour; sometimes maybe I'll be walking at only 1.2 miles per hour. The rate is going to fluctuate according to the length and speed of each step. But over time and distance, I should be averaging about two miles per hour, more or less.

The same thing happens in the plant. How long does it take to solder the wire leads on a transformer? Well, if you get out your stopwatch and time the operation over and over again, you might find that it takes, let's say, 4.3 minutes on the average. But the actual time on any given instance may range between 2.1 minutes up to 6.4 minutes. And nobody in advance can say, "This one will take 2.1 minutes... this one will take 5.8 minutes." Nobody can predict that information.

So what's wrong with that? Nothing as far as I can see. Any- way, we don't have any choice. What else are we going to use in place of an "average" or an "estimate"?

I find I'm almost stepping on the boy in front of me. We've slowed down somewhat. It's because we're climbing a long, fairly steep hill. All of us are backed up behind Herbie.

"Come on, Herpes!" says one of the kids.

Herpes?

"Yeah, Herpes, let's move it," says another.