Little’s Law can help you reduce Customer waiting time

Lean Six Sigma Black Belts use Little’s Law to help reduce Customer waiting time ( Lead time). Little’s Law tells us that we must reduce our WORK-IN-PROCESS ( WIP) and also increase our rate of THROUGHPUT.
Average Lead time = Average WIP / Average Throughput
Improving the FLOW of the process and PULL ( Just-in-time) helps reduce WIP , increase throughput and hence reduce lead time.
For example
WIP = Average 20 customer inquires that a call centre has started but not finished
Throughput rate = Average 40 customers we complete per hour we finish processing
Average Lead time (time per customer) = 30 minutes
NOTE: John D.C. Little’s original law was concerned with number of customers entering and leaving a market ( shop ) L = λ W
Where L = average number of customers in the store λ = average arrival rate W = average time that a customer spends in the store