STATISTICS 402 - Assignment 7 (Due April 15, 2005)
1. Example 7.11 (pages 261-262) in the text describes an experiment about leaf lose in Coleus
plants treated with auxin. Data from the experiment appear on page 281 and are repeated
below.
Deblading
No Yes
24
20
20
17
21
11
23
16
Auxin
Control
Plant
1
2
3
4
Lanolin
5
6
7
8
13
15
14
14
11
11
17
13
Lanolin +
high conc
auxin
9
10
11
12
25
24
15
20
35
33
22
31
Lanolin +
low conc
auxin
13
14
15
16
32
26
21
19
38
33
26
20
(a) What are the response, factors of interest, and experimental units?
(b) What is the whole plot factor? What is the sub-plot factor?
(c) Compute treatment means and factor level means. Present these in a single table.
Construct an ANOVA table. You can use JMP to do the calculations but I want you
to write out the ANOVA table with the appropriate sources of variation (do not include
model but include the terms that make up the model.)
(d) Are there statistically significant differences among the levels of auxin? Report the
appropriate F- and P-values and explain why these support your answer. If there are
significant differences, follow up with an appropriate multiple comparison procedure.
(e) Are there statistically significant differences due to deblading? Report the appropriate
F- and P-values and explain why these support your answer.
(f) Is the interaction between auxin level and deblading statistically significant? Report the
appropriate F- and P-values and explain why these support your answer. Also include
an interaction plot and comment on how this agrees with the statistical test performed.
(g) Reread the description of the experiment in the text. Is there a nuisance factor that
might be confounded with the effect of deblading? How important is this confounding
factor and how should you account for it in interpreting the results of the experiment.