STAT 305B Fall 2007
Homework 2 Due(9/6)
•Reading Assignment: Chapter 2: 2.1, 2.3, 2.4(ignore 2.4.3), 2.5 and Chapter 3: 3.1
•Problem 1: A drug company wanted to test a new indigestion medication. The researchers found
800 adults aged 25-35 and randomly assigned them to two groups. The first group received the new
drug, while the second received a placebo. After one month of treatment, the percentage of each
group whose indigestion symptoms decreased was recorded and compared.
a). Identify the experimental units, experimental variable(s) and response variable(s).
b). What is the purpose of using random assignment?
c). What is the purpose of using placebo for the second group?
d). Name some possible concomitant variable(s) of this study.
•Problem 2: In the situation that is described in Problem 1, the sex(Male or Female) may cause
some heterogeneity within the adults (with respect to the outcome of the experiment).
a). State the idea of “blocking” and describe how “blocking” could be applied in this situation.
b). Compare the approach “blocking” with the one that is applied in Problem 1, which one is
expected to be better? Briefly explain your conjecture.
•JMP Practice (Descriptive Statistics of data in Table 3.1 (Page 67)), then complete Problem 3 on
next page.
1. Launch JMP and load data from the text CD or download them from the book companion
website. The dataset in Table 3.1 is the Prob 2.jmp in the folder “Section 1” under “Chapter
3”.
2. Display the descriptive statistics for 230G and 200G.
(a) From the JMP interface, select “Analyze→Distribution.”
(b) In the dialog box that follows, click the column name “230G”; then click “Y, Columns”
to add 230G to the list of columns to be analyzed.
(c) Click the column name “200G” and click “Y, Columns” to add 200G to the list of columns
to be analyzed.
(d) Click “OK”.
3. JMP displays descriptive statistics and a frequency distribution for each bullet type.
(a) On top of the output, click the small red triangle(s) below the “Distributions” to see
various options.
(b) Check and un-check the options that we are introducing in class, e.g. Normal Quantile
plot, Stem and Leaf etc..
4. To save the output as graph file that may be included in Word (Or other text editing software).
1
