# 1: Introduction to Data


The topics scientists investigate are as diverse as the questions they ask. However, many of these investigations can be addressed with a small number of data collection techniques, analytic tools, and fundamental concepts in statistical inference. This chapter provides a glimpse into these and other themes we will encounter throughout the rest of the book. We introduce the basic principles of each branch and learn some tools along the way. We will encounter applications from other fields, some of which are not typically associated with science but nonetheless can benefit from statistical study.

• 1.1: Prelude to Introduction to Data
Scientists seek to answer questions using rigorous methods and careful observations. These observations form the backbone of a statistical investigation and are called data. Statistics is the study of how best to collect, analyze, and draw conclusions from data. It is helpful to put statistics in the context of a general process of investigation: Identify a question or problem. Collect relevant data on the topic. Analyze the data. Form a conclusion.
• 1.2: Case Study- Using Stents to Prevent Strokes
Section 1.1 introduces a classic challenge in statistics: evaluating the efficacy of a medical treatment. Terms in this section, and indeed much of this chapter, will all be revisited later in the text. The plan for now is simply to get a sense of the role statistics can play in practice.
• 1.3: Data Basics
Effective presentation and description of data is a first step in most analyses. This section introduces one structure for organizing data as well as some terminology that will be used throughout this book.
• 1.4: Overview of Data Collection Principles
The first step in conducting research is to identify topics or questions that are to be investigated. A clearly laid out research question is helpful in identifying what subjects or cases should be studied and what variables are important. It is also important to consider how data are collected so that they are reliable and help achieve the research goals.
• 1.5: Observational Studies and Sampling Strategies
Generally, data in observational studies are collected only by monitoring what occurs, what occurs, while experiments require the primary explanatory variable in a study be assigned for each subject by the researchers. Making causal conclusions based on experiments is often reasonable. However, making the same causal conclusions based on observational data can be treacherous and is not recommended. Thus, observational studies are generally only sufficient to show associations.
• 1.6: Experiments
Studies where the researchers assign treatments to cases are called experiments. When this assignment includes randomization, e.g. using a coin ip to decide which treatment a patient receives, it is called a randomized experiment. Randomized experiments are fundamentally important when trying to show a causal connection between two variables.
• 1.7: Examining Numerical Data
In this section we will be introduced to techniques for exploring and summarizing numerical variables. Recall that outcomes of numerical variables are numbers on which it is reasonable to perform basic arithmetic operations.
• 1.8: Considering Categorical Data
Like numerical data, categorical data can also be organized and analyzed. In this section, we will introduce tables and other basic tools for categorical data that are used throughout this book.
• 1.9: Case Study- Gender Discrimination (Special Topic)
Statisticians are sometimes called upon to evaluate the strength of evidence.
• 1.E: Introduction to Data (Exercises)
Exercises for Chapter 1 of the "OpenIntro Statistics" textmap by Diez, Barr and Çetinkaya-Rundel.

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