The Limit Distribution of level Crossings of a Random Walk, and a Simple Unit Root Test
推导了连续增量随机游走水平穿越次数的极限分布，并探讨了用穿越频率检验单位根的方法。
We derive the limit distribution of the number of crossings of a level by a random walk with continuously distributed increments, using a Brownian motion local time approximation. This complements the well-known result for the random walk on the integers. Use of the frequency of level crossings to test for a unit root is examined.