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"If the first step finishes in eight days, when will the second step start?" I repeat my question.

A light is coming on in Ted's eyes. "It will start when it was originally planned to," he confidently states, and smiles.

"Why?"

"Because the team that finished ahead of time won't report it. You see, the way we are set up, there is no reward for finishing early, but there is, in fact, a big penalty." And he explains, "If you finish early you just invite pressure from management to cut the times. Your friends, in charge of other similar teams, will not like it, to say the least."

"So what will happen?"

"They will find ways to play with it. Don't worry, if they don't want you to find out that they finished, you won't."

As a second thought he adds, "Besides, even in the unlikely event that they do report it, it doesn't mean that the second step will immediately start. That team is probably busy doing something else, they might even be at another site."

"Another site, hmm . . ." Ted's explanation is tied too strongly to his specific environment, the construction industry. I'm afraid that my students won't see how general these phenomena are. That's why I ask, "Do we find this type of behavior in other industries?"

"Definitely," Charlie is firm. "Even though not exactly for the same reasons. A programmer is not afraid of his peer's reaction, but as I already mentioned, it will not cross his mind to say that he finished ahead of time. He or she will always find something in the program that can still be polished a little more."

"And if they report an early finish?" I encourage him to continue.

"Still not much will happen. The person who is supposed to do the next step knows that there is sufficient time, so what's the rush?"

"Let me see. What both of you are telling us is that it is likely that an early finish will not be reported. And even if it is, frequently the time gained will not be taken advantage of by the next step; it will just be wasted."

I write on the board: "A delay in one step is passed, in full, to the next step. An advance made in one step is usually wasted."

There were many other comments, but the conclusions held.

"You see what it means?" I try to drive home the message. "In sequential steps our deviations do not average out. Delays accumulate, while advances do not. This can explain how so much of our safety disappears."

I let them think about it a little, and then proceed. "What happens in the case of parallel steps?"

I draw four boxes all leading to one. "Suppose that in three of these steps we were early by five days. And in one step we were late by fifteen days. Statistically, if we average out all four boxes, we are on time."

The class bursts out laughing.

"In the case of parallel steps, and in any project there are many of them, the biggest delay is passed on to the next step. All other early finishes do not count at all."

"What you are telling us," Ruth is thinking hard, "is that most of the safety we put in doesn't help at all."

"Correct."

"If we could find a way to put the safety only where it's needed..."

Ted can't control his impatience. Mockingly he says, "If we had a crystal ball that would tell us, in advance, exactly where the problems would occur, then . . . Come on Ruth, let's be realistic."

Ruth blushes a little, but she is not going to be bullied. "Still, let's face what we see here. The only thing that counts is the performance of the project as a whole. At the end, it doesn't matter how many steps were not completed on time, as long as the project was delivered when promised. And what do we do? We try to protect the performance of each step. Most of this protection is wasted. So even though we put in that much safety, the project as a whole is exposed."

Ruth's words trigger a train of thought in my head. "We try to protect the performance of each step." That sounds to me like a cost world mentality. "The only thing that counts is the performance of the project as a whole." That