430 Statistical Methods
of the Octel fi lter were at least equal to
those of standard silencers.
a. Open the Noise workbook from the
Chapter10 data folder and save it as
Noise ANOVA.
b. Create boxplots and histograms of the
Noise variable, broken down by the
Size_Type variable (you should edit
the labels in the boxplot to make the
plot easier to read).
c. Create an interaction plot of the Noise
variable for different levels of the Size
and Type factors. Is there evidence of
an interaction from the plot?
d. Create a two-way table of the Noise
data for the Size and Type factors.
e. Using the two-way table, perform a
two-way ANOVA on the data. What
factors are signifi cant?
f. Save your changes to the workbook
and write a report summarizing your
conclusions.- The Waste workbook contains data from
a clothing manufacturer. The fi rm’s qual-
ity control department collects weekly
data on percent waste, relative to what
can be achieved by computer layouts of
patterns on cloth. A negative value indi-
cates that the plant employees beat the
computer in controlling waste. Your job
is to determine whether there is a sig-
nifi cant difference among the fi ve plants
in their percent waste values.
a. Open the Waste workbook from the
Chapter10 folder and save it as Waste
ANOVA.
b. Create boxplots of the waste value for
the fi ve plants. Are there any extreme
outliers in the data that you should be
concerned about?
c. Perform a one-way analysis of vari-
ance on the data.
d. Create a matrix of paired mean differ-
ences for the data. State your tentative
conclusions.
e. Copy the waste data to another work-
sheet in the workbook, and delete any
observations that were identifi ed as
extreme outliers on the boxplots.
f. Redo your one-way ANOVA and
means matrix on the revised data.
Have your conclusions changed?
g. Save your workbook and write a re-
port summarizing your fi ndings.- Cuckoos lay their eggs in the nests of
other host birds. The host birds adopt
and then later hatch the eggs. The Eggs
workbook contains data on the lengths
of eggs found in the nest of host birds.
One theory holds that cuckoos lay their
eggs in the nests of a particular host
species and that they mate within a de-
fi ned territory. If true, this would cause
a geographical subspecies of cuckoos
to develop and natural selection would
ensure the survival of cuckoos most fi t-
ted to lay eggs that would be adopted by
a particular host. If cuckoo eggs differed
in length between hosts, this would lend
some weight to that hypothesis. You’ve
been asked to compare the length of the
eggs placed in the different nests of the
host birds.
a. Open the Eggs workbook from the
Chapter10 folder and save it as Eggs
ANOVA.
b. Perform a one-way ANOVA on the
egg lengths for the six species. Is there
evidence that the egg lengths differ
between the species?
c. Create a boxplot of the egg lengths.
d. Analyze the pairwise differences be-
tween the species by creating a means
matrix. Use the Bonferroni correction
on the p values. What, if any, differ-
ences do you see between the species?
e. Save your changes to the workbook
and write a report summarizing your
observations.