This chapter introduces the key statistical concepts that are necessary to understand and analyze high-energy astronomical data. Our goal is to present enough information such that a reader may learn to judge the quality of their inferences and properly evaluate claims made in the literature. We first describe the role played by statistical methodology in analysis in Sect. 6.1. We then introduce the Poisson likelihood, which governs how counts fluctuations are described, in the context of several other useful distributions, in Sect. 6.2. Methods to determine and propagate uncertainties are discussed in Sect. 6.3. This is followed by a discussion of model fitting in Sect. 6.4, followed by hypothesis tests and model comparisons in Sect. 6.5. We list some targeted references from astronomical literature, and some books for further reading, in Sect. 6.6.