1. Explain the differences between categorical, ordinal, interval, and ratio data. 2. Explain the difference between cross‐sectional and time‐series data. 3. What is the Six Sigma initiative? 4. What is the difference between a population and a sample? 5. List the different types of charts available in Excel and explain characteristics of data sets that make each chart most appropriate to use. 6. What kind of graphical displays are appropriate for representing the frequencies of several mutually exclusive categories? What are the options for representing such data over the levels of another variable, such as year, gender or race?