Analyze each of the following arguments in terms of the variation of the “phenomena” to show how they follow the pattern of the method of concomitant variation:

Stanley Coren sought to plumb the connections between sleeplessness and accidents. To do that he focused on the yearly shift to daylight time in eastern North America, when (because clocks are moved forward one hour) most people lose an hour of sleep. He compared the number of accidents then with the number on normal days, and found that on the day after the time change, in Canada, there was an 8 percent increase in accidents. Then, examining the day after the return to standard time, when people gain an hour of sleep, he found a corresponding decrease in accidents. “What we’re looking at,” says the Director of the Human Chronobiology Laboratory at the University of Pittsburgh, commenting upon Soren’s results, “is national jet lag.”
—S. Coren, Sleep Thieves (New York: The Free Press, 1996)