As part of the study described in Exercise 3.1, the experimenters obtained the same kind of data from a smaller group who had read the passage before answering the questions (called the Passage group). Their data follow.

66 75 72 71 55 56 72 93 73 72 72 73 91 66 71 56 59

(a) What can you tell just by looking at these numbers? Do students do better when they have read the passage?

(b) Plot these data on one side of a stem-and-leaf display and the NoPassage data on the other side of the same stem-and-leaf display.

(c) What can you see by looking at this stem-and-leaf display?

(d) A further discussion of this example can be found at http://www.uvm.edu/~dhowell/fundamentals7/Katzfolder/katz.html although it also covers material that we will discuss later in this book.