Suppose You Want to Estimate the Average Waiting Time at the Coffee

Short Answer

Suppose you want to estimate the average waiting time at the coffee bar on campus. You decide to choose five days of the semester at random and then visit the coffee bar at four randomly chosen times on those days. You will record the waiting time for the customers who you find in line at those times and then calculate the average of these times.
-Even though your sampling process involves multiple stages of randomness, it is still biased. Explain why and in which direction.