[R] F-test where the coefficients in the H_0 is nonzero

[peter dalgaard]

The null hypothesis is different (and the different numerator Df is the givaway).

> lm0 <- lm(y~-1, df1)
> anova(lm0,lm1)
Analysis of Variance Table

Model 1: y ~ -1
Model 2: y ~ x
  Res.Df   RSS Df Sum of Sq      F Pr(>F)
1      3 149.0                           
2      1   1.5  2     147.5 49.167 0.1003

-pd

> On 9 Aug 2018, at 10:58 , John <miaojpm using gmail.com> wrote:
> 
> Hi,
> 
>   I try to run the same f-test by lm (with summary) and the function
> "linearHypothesis" in car package. Why are the results (p-values for the
> f-test) different?
> 
> 
>> df1<-data.frame(x=c(2,3,4), y=c(7,6,8))
>> lm1<-lm(y~x, df1)
>> lm1
> 
> Call:
> lm(formula = y ~ x, data = df1)
> 
> Coefficients:
> (Intercept)            x
>        5.5          0.5
> 
>> summary(lm1)
> 
> Call:
> lm(formula = y ~ x, data = df1)
> 
> Residuals:
>   1    2    3
> 0.5 -1.0  0.5
> 
> Coefficients:
>            Estimate Std. Error t value Pr(>|t|)
> (Intercept)    5.500      2.693   2.043    0.290
> x              0.500      0.866   0.577    0.667
> 
> Residual standard error: 1.225 on 1 degrees of freedom
> Multiple R-squared:   0.25, Adjusted R-squared:   -0.5
> F-statistic: 0.3333 on 1 and 1 DF,  p-value: 0.6667
> 
>> linearHypothesis(lm1, c("(Intercept)=0", "x=0"))
> Linear hypothesis test
> 
> Hypothesis:
> (Intercept) = 0
> x = 0
> 
> Model 1: restricted model
> Model 2: y ~ x
> 
>  Res.Df   RSS Df Sum of Sq      F Pr(>F)
> 1      3 149.0
> 2      1   1.5  2     147.5 49.167 0.1003
> 
> 2018-08-03 13:54 GMT+08:00 Annaert Jan <jan.annaert using uantwerpen.be>:
> 
>> You can easily test linear restrictions using the function
>> linearHypothesis() from the car package.
>> There are several ways to set up the null hypothesis, but a
>> straightforward one here is:
>> 
>>> library(car)
>>> x <- rnorm(10)
>>> y <- x+rnorm(10)
>>> linearHypothesis(lm(y~x), c("(Intercept)=0", "x=1"))
>> Linear hypothesis test
>> 
>> Hypothesis:
>> (Intercept) = 0
>> x = 1
>> 
>> Model 1: restricted model
>> Model 2: y ~ x
>> 
>>  Res.Df     RSS Df Sum of Sq      F Pr(>F)
>> 1     10 10.6218
>> 2      8  9.0001  2    1.6217 0.7207 0.5155
>> 
>> 
>> Jan
>> 
>> From: R-help <r-help-bounces using r-project.org> on behalf of John <
>> miaojpm using gmail.com>
>> Date: Thursday, 2 August 2018 at 10:44
>> To: r-help <r-help using r-project.org>
>> Subject: [R] F-test where the coefficients in the H_0 is nonzero
>> 
>> Hi,
>> 
>>   I try to run the regression
>>   y = beta_0 + beta_1 x
>>   and test H_0: (beta_0, beta_1) =(0,1) against H_1: H_0 is false
>>   I believe I can run the regression
>>   (y-x) = beta_0 +beta_1‘ x
>>   and do the regular F-test (using lm functio) where the hypothesized
>> coefficients are all zero.
>> 
>>   Is there any function in R that deal with the case where the
>> coefficients are nonzero?
>> 
>> John
>> 
>>        [[alternative HTML version deleted]]
>> 
>> ______________________________________________
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>> posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>> 
>> 
>> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Office: A 4.23
Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com