|
|
|
||||
|
|
|||||
Linear Contrasts on page 209 using the data file friendly. Stata does not have a built-in contrast command; however, ATS has developed a program that will do ANOVA contrasts. You can download contrast from within Stata by typing findit contrast (see How can I use the findit command to search for programs and get additional help? for more information about using findit).
use http://www.ats.ucla.edu/stat/stata/examples/ara/friendly, clear
(From Fox, Applied Regression Analysis. Use 'notes' command for source of data)
encode(cond), gen(mycond)
codebook mycond
mycond ------------------------------------------------- Experimental Condition
type: numeric (long)
label: mycond
range: [1,3] units: 1
unique values: 3 coded missing: 0 / 30
tabulation: Freq. Numeric Label
10 1 Before
10 2 Meshed
10 3 SFR
sort mycond
by mycond: summarize correct
-> mycond= Before
Variable | Obs Mean Std. Dev. Min Max
---------+-----------------------------------------------------
correct | 10 36.6 5.337498 24 40
-> mycond= Meshed
Variable | Obs Mean Std. Dev. Min Max
---------+-----------------------------------------------------
correct | 10 36.6 3.025815 30 40
-> mycond= SFR
Variable | Obs Mean Std. Dev. Min Max
---------+-----------------------------------------------------
correct | 10 30.3 7.334091 21 39
anova correct mycond, class(mycond)
Number of obs = 30 R-squared = 0.2433
Root MSE = 5.52067 Adj R-squared = 0.1873
Source | Partial SS df MS F Prob > F
-----------+----------------------------------------------------
Model | 264.60 2 132.30 4.34 0.0232
|
mycond | 264.60 2 132.30 4.34 0.0232
|
Residual | 822.90 27 30.4777778
-----------+----------------------------------------------------
Total | 1087.50 29 37.50
contrast mycond, values( -0.5 -0.5 1)
Contrast variable mycond (-.5 -.5 1)
source SS df MS Dep Var = correct
---------+--------------------------------- N of obs = 30
contrast | 264.6 1 264.6000 F = 8.68
error | 822.9 27 30.4778 Prob > F = 0.0065
---------+---------------------------------
contrast mycond, values( 1 -1 0)
Contrast variable mycond (1 -1 0)
source SS df MS Dep Var = correct
---------+--------------------------------- N of obs = 30
contrast | 0 1 0.0000 F = 0.00
error | 822.9 27 30.4778 Prob > F = 1.0000
---------+---------------------------------
Calculation on page 214 and on page 222 using data file duncan.
use http://www.ats.ucla.edu/stat/stata/examples/ara/duncan.dta, clear
(From Fox, Applied Regression Analysis. Use 'notes' command for source of data)
set matsize 50
gen c=1
mkmat c income educ, matrix(X)
mkmat prestige, matrix(y)
matrix b=inv(X'*X)*X'*y
matrix list b
b[3,1]
prestige
c -6.0646629
income .59873282
educ .54583391
Calculation on page 222.
matrix r=y-X*b
matrix v=(r'*r)/42
matrix V2=v*inv(X'*X)
matrix d=diag(vecdiag(V2))
matrix a=cholesky(d)
matrix list a
symmetric a[3,3]
c income educ
c 4.2719412
income 0 .11966735
educ 0 0 .09825264
UCLA Researchers are invited to our Statistical Consulting Services
We recommend others to our list of Other Resources for Statistical Computing Help
These pages are Copyrighted (c) by UCLA Academic Technology Services