Animal Manure and Mortality Management
Arkansas Swine Odor Survey - Data Analysis
Odor Level Comparisons By Class
An example of the tables used to do pair-wise comparisons between the various
classes is given below. At the top of each table is information on the classes
under investigation and the source of odors. In this example the classes deal
with the overall appearance of the farms. The odor measurements under
consideration are for odors from the facility. There are columns and rows for
each class, which in this example are defined as Poor, Fair, Good, and Very
Good.
The first table presents the results of statistical tests to determine if the
mean and variances of the measured odor ranks for each class are statistically
different from the other classes. There is a row and column for each class
allowing for all possible combinations of the various classes. As this format
provides duplication in comparisons, the results are only presented in the area
below a diagonal line from the upper left to the lower right. A value of "M"
indicates that there is a significant difference between the means of the two
classes being compared. A difference in the variation from the means is
indicated by a "V." The absence of an "M" or a "V" indicates that no significant
differences were found. The statistical tests performed were a two-tailed t-test
for the means and an F-test for the variances. Both tests used an a level of
.05.
The second table provides summary information on the odor measurements for
each class. There are columns for the number, minimum, and maximum of the odor
measurements. There are three columns that indicate the "central" point of the
distribution of the odor ranks. The mean, or average value, is defined as the
sum of all the values divided by the number of values. The median (med) value is
the middle value if all the measurements are placed in ascending order. The mode
(mod) is the most frequently occurring value. The standard deviation (Std) is a
measure of how much variation there is in the set of measurements. Larger Std
values indicate greater variation. The number of times a measurement was made
for each odor rank is also presented on a percentage basis.
Significant Difference
Matrix
Class: Appearance
Odor Source: Facility |
| |
Poor |
Fair |
Good |
Very Good |
Poor |
|
|
|
|
Fair |
M |
|
Duplication Area |
|
Good |
M V |
V |
|
|
Very Good |
M |
|
M |
|
Odor Rank
Distribution Summary
Class: Appearance
Odor Source: Facility |
| |
|
|
|
|
|
|
|
Rank Occurrence Frequency |
Type |
Num |
Min |
Max |
Mean |
Med |
Mod |
Std |
1 |
2 |
3 |
4 |
Poor |
31 |
1 |
3 |
1.85 |
2 |
1 |
0.78 |
38.71% |
32.26% |
29.03% |
0.00% |
Fair |
155 |
1 |
4 |
1.52 |
1 |
1 |
0.72 |
60.65% |
24.52% |
13.55% |
1.29% |
Good |
200 |
1 |
3.5 |
1.39 |
1 |
1 |
0.65 |
69.00% |
21.00% |
9.50% |
0.50% |
Very Good |
220 |
1 |
4 |
1.53 |
1 |
1 |
0.70 |
55.91% |
33.64% |
9.09% |
1.36% |
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Arkansas Swine Odor Survey
|
