Agriculture Reference
In-Depth Information
left side of most keyboards and the close quote is located on the right
of the keyboard between the semicolon and return keys. It is impor-
tant to use these specific keys, unlike normal computer use where the
open and close quotes used are the same key.
he
anova
`depend'
`indep1'
`r e p',
partial
uses all
three variables passed to the program to calculate an analysis of vari-
ance. The sequence of arguments when using this program is impor-
tant. The first argument (
depend
) is considered the dependent
variable, while the
indep1
and
rep
are independent variables. I do a
lot of variety trial evaluations with vegetables, which are usually in an
RCBD (randomized complete block design). So, for me, the
indep1
macro is for the variety list and the
rep
is the replication.
The next four lines create four macros (
v
,
w
,
x
, and
y
) that are val-
ues from the analysis of variance. Just as there were values saved after
the
summarize
command, there are values saved after the
anova
command. he
summarize
command is an r-class command, while
anova
is an e-class command. To see the saved results after an analy-
sis of variance, type
ereturn list
This returns several scalars as well as other information. The scalars
we are interested in using include
e(rmse)
, which is the root mean
square error from the most recent analysis of variance. The square of
this value is the residual mean square. The
e(df _ 2)
is the degrees
of freedom for the replications and adding 1 to this is then the number
of replications, and, finally, the
e(df _ r)
is the residual degrees of
freedom.
The next line calculates the Least Significant Difference (LSD) at
the 5% level. The formula for this calculation is
2
MSE
n
LSDt
=
crit
.
he
t
crit.
value is the critical value of Student's t that can be found
in tables at the back of statistics textbooks. Stata has a function to
calculate this value:
invttail(
n,p
)
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