This is a short chapter but don't be fooled. There is a lot of important concepts introduced here. Pay attention to the following:

• The difference between observation and experimental studies.
• The difference between the two methods of controlling crucial factors in experiments.
• The list of items that should be included in a experimental plan.
• The definition of treatment and factor. Can you give examples from your field of study at to what is a factor and what is a treatment?
• Can you give an example of a factorial set of treatments?
• What is a control treatment and why is it important in most experimental studies.
• What is an experimental unit? How is it different from the measurement unit?
• What do we mean by replication of a treatment in an experiment?
• Is "experimental error" really a mistake?
• What is the important role of the measurement of the variance of the experimental error (OK - I prefer to use the term residual)?
• What do we mean when we talk about "control"?
• What is a block, and why is it an important tool in experimental design?
• What is a covariate?
• Does it make a difference if we talk about randomizing treatments to experimental units or randomly assigning experimental units to treatments?
• Do you understand how to do this randomization?
• What is the difference in randomization between a completely randomized design and a randomized complete block design?
• If I have more experimental units in a block than I have treatments, what do I do about randomization?(see page 844)
• Do you understand how to use the equation for number of replicates on page 845?

Answers to all these questions are in this chapter.