We use statistical analyses to test our predictions using the measures we collect for our sample. Like all aspects of study design, we need to think carefully about our choice of analytical approach. Planning our data analysis in detail, before we collect your data, helps to determine what data we need to collect. It is very common to rush past the analysis plan and dive straight into collecting data. This is partly because statistics are not intuitive and can be intimidating. However, statistical analysis is an integral part of study design. We must understand statistics to understand the strengths, limitations, and potential biases of any research. This may seem daunting, but our understanding of statistics determines the quality of a study. The more we think about this now, the better our study will be. I begin this chapter with how to determine what sort of analyses we need and the need to consult a statistician when we design a study. Next, I cover problems associated with multiple testing and assessing multiple predictor variables. I explain how to prepare an analysis plan and suggest pre-registration.