Agriculture Reference
In-Depth Information
variety | 741.75 3 247.25 9.63 0.0001
date | 1877.625 2 938.8125 36.57 0.0000
variety#date | 847.375 6 141.229167 5.50 0.0005
|
Residual | 847.083333 33 25.6691919
-------------+--------------------------------------------------
Total | 4391.25 47 93.4308511
When dealing with two factors (in this case, varieties and sowing
dates) to show the interaction between these terms, the
#
character is
used between these two factors to calculate the interaction effect. All
three—
variety
,
date
, and
variety#date
—are significant. At
this point, you would want to explore this interaction further. To do
this, you may wish to look at the mean seedstem values for the variet-
ies and dates. Enter the following command:
table
variety date,
contents
(
mean
seedstem)
This results in the following output:
--------------------------------------
Varieties: |
1-Pegasus, |
2-Swt. |
Vidalia, | Sowing date: 1-5 Oct,
3-Nirvana, | 2-15 Oct, 3-29 Oct
4-PS 7092 | 5 Oct 15 Oct 29 Oct
--------------+-----------------------
Pegasus | 9.25 .25 0
Sweet Vidalia | 30.75 5 0
Nirvana | 7 0 .25
PS 7092 | 8.75 .25 0
--------------------------------------
This shows that, as the sowing date gets later, there appears to be
a reduction in the number of seedstems. In addition, Sweet Vidalia
appears to have more seedstems than the other varieties, at least for
the first and second sowing dates. This can be explored further by
examining ANOVA tables for varieties over the different sowing dates
as well as evaluating ANOVA tables for the different sowing dates for
each variety. For the former case, enter the following command:
by
date,
sort
:
anova
seedstem rep variety
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