# Anova

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##### Anova Tables for Various Statistical Models

Calculates type-II or type-III analysis-of-variance tables for model objects produced by lm, glm, multinom (in the nnet package), and polr (in the MASS package). For linear models, F-tests are calculated; for generalized linear models, likelihood-ratio chisquare, Wald chisquare, or F-tests are calculated; for multinomial logit and proportional-odds logit models, likelihood-ratio tests are calculated. Various test statistics are provided for multivariate linear models produced by lm or manova.

Keywords
models, regression, htest
##### Usage
Anova(mod, ...)

Manova(mod, ...)

## S3 method for class 'lm':
Anova(mod, error, type=c("II","III", 2, 3), ...)

## S3 method for class 'aov':
Anova(mod, ...)

## S3 method for class 'glm':
Anova(mod, type=c("II","III", 2, 3),
test.statistic=c("LR", "Wald", "F"),
error, error.estimate=c("pearson", "dispersion", "deviance"), ...)

## S3 method for class 'multinom':
Anova(mod, type = c("II","III", 2, 3), ...)

## S3 method for class 'polr':
Anova(mod, type = c("II","III", 2, 3), ...)

## S3 method for class 'mlm':
Anova(mod, type=c("II","III", 2, 3), SSPE, error.df,
idata, idesign, icontrasts=c("contr.sum", "contr.poly"),
test.statistic=c("Pillai", "Wilks", "Hotelling-Lawley", "Roy"),...)

## S3 method for class 'manova':
Anova(mod, ...)

## S3 method for class 'mlm':
Manova(mod, ...)

## S3 method for class 'Anova.mlm':
print(x, ...)

## S3 method for class 'Anova.mlm':
summary(object, test.statistic, multivariate=TRUE,
univariate=TRUE, digits=unlist(options("digits")), ...)
##### Arguments
mod
lm, aov, glm, multinom, polr or mlm model object.
error
for a linear model, an lm model object from which the error sum of squares and degrees of freedom are to be calculated. For F-tests for a generalized linear model, a glm object from which the dispersion is to be e
type
type of test, "II", "III", 2, or 3.
test.statistic
for a generalized linear model, whether to calculate "LR" (likelihood-ratio), "Wald", or "F" tests. For a multivariate linear model, the multivariate test statistic to compute --- one of "Pillai
error.estimate
for F-tests for a generalized linear model, base the dispersion estimate on the Pearson residuals (pearson, the default); use the dispersion estimate in the model object (dispersion), which, e.g., is fixed to 1 for
SSPE
The error sum-of-squares-and-products matrix; if missing, will be computed from the residuals of the model.
error.df
The degrees of freedom for error; if missing, will be taken from the model.
idata
an optional data frame giving a factor or factors defining the intra-subject model for multivariate repeated-measures data. See Details for an explanation of the intra-subject design and for further explanation of the other argume
idesign
a one-sided model formula using the data'' in idata and specifying the intra-subject design.
icontrasts
names of contrast-generating functions to be applied by default to factors and ordered factors, respectively, in the within-subject data''; the contrasts must produce an intra-subject model matrix in which different terms are orthogonal.
x, object
object of class "Anova.mlm" to print or summarize.
multivariate, univariate
print multivariate and univariate tests for a repeated-measures ANOVA; the default is TRUE for both.
digits
minimum number of significant digits to print.
...
arguments to be passed to linear.hypothesis; only use white.adjust for a linear model.
##### Details

The designations "type-II" and "type-III" are borrowed from SAS, but the definitions used here do not correspond precisely to those employed by SAS. Type-II tests are calculated according to the principle of marginality, testing each term after all others, except ignoring the term's higher-order relatives; so-called type-III tests violate marginality, testing each term in the model after all of the others. This definition of Type-II tests corresponds to the tests produced by SAS for analysis-of-variance models, where all of the predictors are factors, but not more generally (i.e., when there are quantitative predictors). Be very careful in formulating the model for type-III tests, or the hypotheses tested will not make sense. As implemented here, type-II Wald tests for generalized linear models are actually differences of Wald statistics. For tests for linear models, multivariate linear models, and Wald tests for generalized linear models, Anova finds the test statistics without refitting the model. The standard R anova function calculates sequential ("type-I") tests. These rarely test interesting hypotheses. A MANOVA for a multivariate linear model (i.e., an object of class "mlm" or "manova") can optionally include an intra-subject repeated-measures design. If the intra-subject design is absent (the default), the multivariate tests concern all of the response variables. To specify a repeated-measures design, a data frame is provided defining the repeated-measures factor or factors via idata, with default contrasts given by the icontrasts argument. An intra-subject model-matrix is generated from the formula specified by the idesign argument; columns of the model matrix corresponding to different terms in the intra-subject model must be orthogonal (as is insured by the default contrasts). Note that the contrasts given in icontrasts can be overridden by assigning specific contrasts to the factors in idata. Manova is essentially a synonym for Anova for multivariate linear models.

##### Value

• An object of class "anova", or "Anova.mlm", which usually is printed. For objects of class "Anova.mlm", there is also a summary method, which provides much more detail than the print method about the MANOVA, including traditional mixed-model univariate F-tests with Greenhouse-Geisser and Hunyh-Feldt corrections.

##### Warning

Be careful of type-III tests.

##### References

Fox, J. (1997) Applied Regression, Linear Models, and Related Methods. Sage. Hand, D. J., and Taylor, C. C. (1987) Multivariate Analysis of Variance and Repeated Measures: A Practical Approach for Behavioural Scientists. Chapman and Hall. O'Brien, R. G., and Kaiser, M. K. (1985) MANOVA method for analyzing repeated measures designs: An extensive primer. Psychological Bulletin 97, 316--333.

linear.hypothesis, anova anova.lm, anova.glm, anova.mlm

##### Aliases
• Anova
• Anova.lm
• Anova.aov
• Anova.II.lm
• Anova.III.lm
• Anova.glm
• Anova.II.F.glm
• Anova.II.LR.glm
• Anova.II.Wald.glm
• Anova.III.F.glm
• Anova.III.LR.glm
• Anova.III.Wald.glm
• Anova.multinom
• Anova.II.multinom
• Anova.III.multinom
• Anova.polr
• Anova.II.polr
• Anova.III.polr
• Anova.mlm
• Anova.manova
• Manova
• Manova.mlm
• print.Anova.mlm
• summary.Anova.mlm
##### Examples
## Two-Way Anova

mod <- lm(conformity ~ fcategory*partner.status, data=Moore,
contrasts=list(fcategory=contr.sum, partner.status=contr.sum))
Anova(mod)
## Anova Table (Type II tests)
##
## Response: conformity
##                         Sum Sq Df F value   Pr(>F)
## fcategory                 11.61  2  0.2770 0.759564
## partner.status           212.21  1 10.1207 0.002874
## fcategory:partner.status 175.49  2  4.1846 0.022572
## Residuals                817.76 39
Anova(mod, type="III")
## Anova Table (Type III tests)
##
## Response: conformity
##                          Sum Sq Df  F value    Pr(>F)
## (Intercept)              5752.8  1 274.3592 < 2.2e-16
## fcategory                  36.0  2   0.8589  0.431492
## partner.status            239.6  1  11.4250  0.001657
## fcategory:partner.status  175.5  2   4.1846  0.022572
## Residuals                 817.8 39

## One-Way MANOVA
## See ?Pottery for a description of the data set used in this example.

summary(Anova(lm(cbind(Al, Fe, Mg, Ca, Na) ~ Site, data=Pottery)))

## Type II MANOVA Tests:
##
## Sum of squares and products for error:
##            Al          Fe          Mg          Ca         Na
## Al 48.2881429  7.08007143  0.60801429  0.10647143 0.58895714
## Fe  7.0800714 10.95084571  0.52705714 -0.15519429 0.06675857
## Mg  0.6080143  0.52705714 15.42961143  0.43537714 0.02761571
## Ca  0.1064714 -0.15519429  0.43537714  0.05148571 0.01007857
## Na  0.5889571  0.06675857  0.02761571  0.01007857 0.19929286
##
## ------------------------------------------
##
## Term: Site
##
## Sum of squares and products for the hypothesis:
##             Al          Fe          Mg         Ca         Na
## Al  175.610319 -149.295533 -130.809707 -5.8891637 -5.3722648
## Fe -149.295533  134.221616  117.745035  4.8217866  5.3259491
## Mg -130.809707  117.745035  103.350527  4.2091613  4.7105458
## Ca   -5.889164    4.821787    4.209161  0.2047027  0.1547830
## Na   -5.372265    5.325949    4.710546  0.1547830  0.2582456
##
## Multivariate Tests: Site
##                        Df test stat  approx F   num Df   den Df     Pr(>F)
## Pillai            3.00000   1.55394   4.29839 15.00000 60.00000 2.4129e-05 ***
## Wilks             3.00000   0.01230  13.08854 15.00000 50.09147 1.8404e-12 ***
## Hotelling-Lawley  3.00000  35.43875  39.37639 15.00000 50.00000 < 2.22e-16 ***
## Roy               3.00000  34.16111 136.64446  5.00000 20.00000 9.4435e-15 ***
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

## MANOVA for a randomized block design (example courtesy of Michael Friendly:
##  See ?Soils for description of the data set)

soils.mod <- lm(cbind(pH,N,Dens,P,Ca,Mg,K,Na,Conduc) ~ Block + Contour*Depth,
data=Soils)
Manova(soils.mod)

## Type II MANOVA Tests: Pillai test statistic
##                Df test stat approx F num Df den Df    Pr(>F)
## Block           3    1.6758   3.7965     27     81 1.777e-06 ***
## Contour         2    1.3386   5.8468     18     52 2.730e-07 ***
## Depth           3    1.7951   4.4697     27     81 8.777e-08 ***
## Contour:Depth   6    1.2351   0.8640     54    180    0.7311
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

## a multivariate linear model for repeated-measures data
## See ?OBrienKaiser for a description of the data set used in this example.

phase <- factor(rep(c("pretest", "posttest", "followup"), c(5, 5, 5)),
levels=c("pretest", "posttest", "followup"))
hour <- ordered(rep(1:5, 3))
idata <- data.frame(phase, hour)
idata
##       phase hour
## 1   pretest    1
## 2   pretest    2
## 3   pretest    3
## 4   pretest    4
## 5   pretest    5
## 6  posttest    1
## 7  posttest    2
## 8  posttest    3
## 9  posttest    4
## 10 posttest    5
## 11 followup    1
## 12 followup    2
## 13 followup    3
## 14 followup    4
## 15 followup    5

mod.ok <- lm(cbind(pre.1, pre.2, pre.3, pre.4, pre.5,
post.1, post.2, post.3, post.4, post.5,
fup.1, fup.2, fup.3, fup.4, fup.5) ~  treatment*gender,
data=OBrienKaiser)
(av.ok <- Anova(mod.ok, idata=idata, idesign=~phase*hour))
## Type II Repeated Measures MANOVA Tests: Pillai test statistic
##                             Df test stat approx F num Df den Df    Pr(>F)
## treatment                    2    0.4809   4.6323      2     10 0.0376868 *
## gender                       1    0.2036   2.5558      1     10 0.1409735
## treatment:gender             2    0.3635   2.8555      2     10 0.1044692
## phase                        1    0.8505  25.6053      2      9 0.0001930 ***
## treatment:phase              2    0.6852   2.6056      4     20 0.0667354 .
## gender:phase                 1    0.0431   0.2029      2      9 0.8199968
## treatment:gender:phase       2    0.3106   0.9193      4     20 0.4721498
## hour                         1    0.9347  25.0401      4      7 0.0003043 ***
## treatment:hour               2    0.3014   0.3549      8     16 0.9295212
## gender:hour                  1    0.2927   0.7243      4      7 0.6023742
## treatment:gender:hour        2    0.5702   0.7976      8     16 0.6131884
## phase:hour                   1    0.5496   0.4576      8      3 0.8324517
## treatment:phase:hour         2    0.6637   0.2483     16      8 0.9914415
## gender:phase:hour            1    0.6950   0.8547      8      3 0.6202076
## treatment:gender:phase:hour  2    0.7928   0.3283     16      8 0.9723693
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

summary(av.ok, multivariate=FALSE)
## Univariate Type II Repeated-Measures ANOVA Assuming Compound Symmetry
##
##                                  SS num Df Error SS den Df       F    Pr(>F)
## treatment                   211.286      2  228.056     10  4.6323  0.037687 *
## gender                       58.286      1  228.056     10  2.5558  0.140974
## treatment:gender            130.241      2  228.056     10  2.8555  0.104469
## phase                       167.500      2   80.278     20 20.8651 1.274e-05 ***
## treatment:phase              78.668      4   80.278     20  4.8997  0.006426 **
## gender:phase                  1.668      2   80.278     20  0.2078  0.814130
## treatment:gender:phase       10.221      4   80.278     20  0.6366  0.642369
## hour                        106.292      4   62.500     40 17.0067 3.191e-08 ***
## treatment:hour                1.161      8   62.500     40  0.0929  0.999257
## gender:hour                   2.559      4   62.500     40  0.4094  0.800772
## treatment:gender:hour         7.755      8   62.500     40  0.6204  0.755484
## phase:hour                   11.083      8   96.167     80  1.1525  0.338317
## treatment:phase:hour          6.262     16   96.167     80  0.3256  0.992814
## gender:phase:hour             6.636      8   96.167     80  0.6900  0.699124
## treatment:gender:phase:hour  14.155     16   96.167     80  0.7359  0.749562
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
##
##
## Greenhouse-Geisser and Huynh-Feldt Corrections
##  for Departure from Compound Symmetry
##
##                              GG eps Pr(>F[GG])
## phase                       0.79953  7.323e-05 ***
## treatment:phase             0.79953    0.01223 *
## gender:phase                0.79953    0.76616
## treatment:gender:phase      0.79953    0.61162
## hour                        0.46028  8.741e-05 ***
## treatment:hour              0.46028    0.97879
## gender:hour                 0.46028    0.65346
## treatment:gender:hour       0.46028    0.64136
## phase:hour                  0.44950    0.34573
## treatment:phase:hour        0.44950    0.94019
## gender:phase:hour           0.44950    0.58903
## treatment:gender:phase:hour 0.44950    0.64634
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
##
##                              HF eps Pr(>F[HF])
## phase                       0.92786  2.388e-05 ***
## treatment:phase             0.92786    0.00809 **
## gender:phase                0.92786    0.79845
## treatment:gender:phase      0.92786    0.63200
## hour                        0.55928  2.014e-05 ***
## treatment:hour              0.55928    0.98877
## gender:hour                 0.55928    0.69115
## treatment:gender:hour       0.55928    0.66930
## phase:hour                  0.73306    0.34405
## treatment:phase:hour        0.73306    0.98047
## gender:phase:hour           0.73306    0.65524
## treatment:gender:phase:hour 0.73306    0.70801
## ---
## Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1
Documentation reproduced from package car, version 1.2-6, License: GPL (>= 2)

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