Module 1 Introduction After completing the online activities for this module, you will be able to 1. Explain the need for data analysis 2. Define the different types of variables 3. Explain the difference between observational studies and experiments 4. Understand the language of hypothesis testing 5. Make decisions from hypothesis tests 1.0 Variability 1.1 Sources of Variability Why is data analysis necessary? What is it about scientific studies and the data they give us that makes statistical analysis so important? As an example, suppose we do a simple study involving some measurements of forearm lengths. Ten students were asked to measure the length of their forearm using a tape measure. Table 1.1 shows the data obtained. Table 1.1 Forearm lengths (cm) of 10 students Sex F M M M F F M F F Forearm 27 29 30 30 27 24 27 28 28 M 30 Why are the 10 values we obtained different numbers? After all, we measured the same quantity, the length of a forearm, each time, so why aren't our measurements all the same? The students are using dif f erent methods to measure their forearms The students have dif f erent forearm lengths A combination of the above