This chapter shows engineering student how to construct and interpret confidence intervals. It also shows about engineering student one method for comparing two system designs using simulation. The chapter introduces engineering student to the notion of a population and the idea of sampling from that population. Regardless of the probability distribution of the population mean, the probability distribution of the sample mean is always normal. The chapter considers a population of packets that will travel through the system. It also considers populations of vectors. Statistical analysis of the data resulting from running a simulation model is a very important step in a simulation study. The chapter also considers the problem of estimating the average delay through the single-server queueing system by using simulation. The population mean is equivalent to the theoretical mean which can be calculated using queueing theory. The standard deviation of this probability distribution is the standard error.